This post was written by guest blogger Saulius Šimčikas with analysis of NHANES survey data by Harry Burdon.

Table of Contents

Summary

Self-identity:

Between 2% and 6% of Americans self-identify as vegetarians.

Results of FooDS surveys indicate that the percentage of self-identified vegetarians has been increasing substantially between the years of 2013 and 2018 (see Graph 1).

Around 60% of people who self-identify as vegetarians in surveys report eating meat1 when asked to list everything they ate during two non-consecutive 24-hour periods.

Consumption:

Around 1% of adults both self-identify as vegetarians and report never consuming meat. It seems that this percentage has not changed substantially since the mid-1990s (see Surveys about both self-identity and consumption).

The percentage of adults who report not consuming any meat on two non-consecutive 24-hour periods seems to have increased between 2003 and 2014 but remained below 2.5% (see Graph 3). If we also consider the people who ate fish in the last 30 days as non-vegetarians, the vegetarianism rate remained below 1.5%. Only ~55% of these people self-identify as vegetarians. 2

Less than 0.4% of adults reported consuming no animal products on two non-consecutive 24-hour periods (see Graph 3).

The percentage of people aged 8 to 18 who report not consuming meat has not changed substantially between 2003 and 2014 (see my analysis of NHANES dietary recall data and VRG youth polls).

The percentage of vegetarians has almost certainly3 increased since 1978, when only 1.2% of people surveyed self-identified as vegetarians and 0.55% self-identified as strict vegetarians.

Surveying:

Online surveys tend to find significantly higher rates of vegetarianism than face-to-face surveys, possibly due to biases in online surveys.

The results of widely cited polls by The Vegetarian Resource Group (VRG) should be compared with each other with caution because they differ from each other in many important aspects (such as survey method, questions, and census-balancing method). What is more, so far they found significantly higher percentages of vegetarians and vegans than other surveys (for unknown reasons).

Even though many studies tried to find the percentage of vegetarians and vegans in the U.S., it is difficult to determine the overall trend by comparing their results because most of them used different questions, surveying methods, sampling methods, etc. There is a need for a longitudinal study that would consistently use the same methodology to ask questions about long-term consumption.4

Introduction

2017 saw the highest per capita egg consumption in the U.S. in over 20 years.5 Per capita red meat and poultry consumption in the U.S. has been increasing as well, and is expected to reach a record high in 2018.6, 7, 8 This does not necessarily indicate a long-term trend, because the recent surge in meat consumption is mostly attributed to an oversupply of chicken and resulting low prices—rather than to increased demand.9

One indication that the demand for animal products in the U.S. may be declining is the apparent rising popularity of vegetarianism and veganism. For example, the number of restaurants in the Vegetarian Journal’s Guide to Vegetarian and Vegan Restaurants in the U.S. and Canada rose from 55 in 1993 to about 971 in 2018. Plant-based food sales in the U.S. recently experienced 8.1% growth in one year.10 Similarly, with the recent success of movies like Okja, it seems that vegan messaging is beginning to break into the mainstream.

Such indirect indicators could be misleading, however. Despite apparently similar trends in the U.K., data from Waters (2018)11 suggests that the percentage of vegetarians and vegans in the U.K. has not changed much over the last 25 years. To find out whether this is changing in the U.S., I searched for all surveys done on this topic and examined their results. I first analyzed studies that asked respondents whether they self-identify as vegetarians. I then examined surveys that also used dietary data. After that, I reviewed surveys about veganism in the same manner. Finally, I analyzed dietary recall data of two 24-hour periods from the National Health and Nutrition Examination Survey. Throughout this blog post, I discuss various reasons to be cautious about inferring too much from the available data and comparing studies that used different surveying methods or questions.

Review of Past Studies

Surveys About Self-Identity

Vegetarians

First, I list in chronological order the surveys that only ask people whether they are vegetarian. All the surveys in the list were presented as if they were nationally representative, although in some cases this was not explicitly mentioned (such surveys are marked with a star next to the sample size figure). The list below is unlikely to be exhaustive, and I have some minor concerns about it not being fully representative.12

The results of the surveys seem very inconsistent. I will examine the bigger surveys in more detail:

Study Year Sample size % Self-identified vegetarians Question Surveying method Nationwide Food Consumption Survey23 1977–1978 37,135 1.2% “Are you a vegetarian?” Face-to-face interviews Continuing Survey of Food Intakes by Individuals (CSFII)24) 1994–1996, 1998 9,854 2.7% “Do you consider (Yourself/NAME) to be a vegetarian?” Face-to-face, combined with a health examination25 July 15, 2002 issue of TIME magazine 2002 10,007 4% “Do you consider yourself a vegetarian?” Online National Health and Nutrition Examination Survey (NHANES)26 2007–2010 11,592 2.3% “Do you consider yourself a vegetarian?” Face-to-face, combined with a health examination27 FooDS surveys 2013–2018 >62,000 5.3% “Are you a vegetarian or a vegan?” 61 online surveys

The tables seem to provide weak evidence that the percentage of self-identified vegetarians is increasing. However, these surveys should be compared with caution. This is because they differ from each other in the following ways:

Surveying method

Selection of the people that they tried to contact, 28

Phrasing of the question about vegetarianism

Questions preceding the question about vegetarianism

Minimum respondent age requirement (although differences are minor) 29

Lack of clarity around whether all of the surveys excluded institutionalized adults

These differences might be the cause for the inconsistencies in the results. For example, some vegans do not consider themselves to be vegetarians and therefore answer the question about vegetarian self-identity negatively, unless it also asks about veganism (like in FooDS surveys).30

We can also notice that online and telephone surveys find significantly higher percentages than face-to-face interviews. This could be due to the different biases that these surveying methods cause. Face-to-face surveys are more susceptible to social desirability bias31 and may be worse at representing busy people.32 On the other hand, it is possible that in CSFII and NHANES surveys the prospect of health examination made people more honest. Online surveys can usually only reach those who have internet access (currently 75–85% of Americans),33 agree to become part of a survey panel, and respond to an invitation to participate. This bias seems to inflate the percentage of vegetarians found in online surveys because both online survey respondents and vegetarians tend to have higher income, be more educated, and be younger.34, 35 Consequently, I’m especially skeptical of the 2002 TIME online survey results, which found the vegetarianism rate to be 4%.36

Issues with online surveys can be somewhat mitigated by giving more weight to answers of respondents who represent a group that would otherwise be underrepresented in the study. For example, FooDS surveys use census-balancing. That is, different weights are assigned to respondents’ responses to match the general U.S. population in terms of age, gender, education, and region of residence.37 However, FooDS surveys still give results nearly two times higher than the results from NHANES surveys.

One possible explanation is that there are differences between online survey respondents and the general population that are not resolved by census-balancing because certain kinds of people are simply more inclined to complete online surveys. A 2012 study conducted in Germany compared telephone and online surveys on different topics and came to a conclusion that even after census-balancing the result of an online survey cannot be labeled as representative.38 Similarly, according to two studies conducted in the early 2000s in the U.K., even after controlling for demographic characteristics online survey respondents tend to be more politically active, travel more, eat out more, and be more knowledgeable and viewpoint-oriented than respondents of face-to-face surveys.39 It seems likely that the vegetarianism rate among them is different as well, but it is unclear how relevant these results are to the present-day United States. Szolnoki and Hoffmann (2013) compared face-to-face, telephone, and online sampling methods and concluded that online sampling is inadvisable for studies that need to be representative.40

However, comparing results of different online surveys can still provide meaningful evidence, especially if they all use the same sampling method, questions, and census-balancing mechanism (like the FooDS surveys that were conducted every month between May 2013 and May 2018). Each of the 61 surveys that have been undertaken so far has a sample size of at least 1,000 individuals. If we take a closer look at their results, we can see an upward trend in the short term:41

This trend in FooDS surveys results seems to provide the most robust evidence that the percentage of self-identified vegetarians is increasing, at least among some subgroups of the population.

Unfortunately, we cannot draw firm conclusions from surveys about self-identity because many people who self-identify as vegetarians actually eat meat:

Some of the people who self-identified as vegetarians in the 1977–1978 Nationwide Food Consumption Survey reported consumption of meat during the three days on which dietary information was obtained. 42

CSFII 1994–1996 asked detailed questions about what the respondents had eaten in the past 24 hours on two separate occasions. Of those who identified as vegetarians, 64% had eaten at least 10g of meat in one or both 24-hour periods.

In the 2002 TIME survey, when asked which type of vegetarian describes them the best, 57% of self-identified vegetarians chose the “semi-vegetarian” option.

survey, when asked which type of vegetarian describes them the best, 57% of self-identified vegetarians chose the “semi-vegetarian” option. According to my analysis, 59% of adults who self-identified as vegetarians in NHANES surveys reported eating meat during the two 24-hour periods for which detailed data was collected. An additional 10% did not report meat consumption during the two dietary recall days but indicated that they ate fish in the last 30 days. Similarly, Juan, Yaminia, & Britten (2015) found that 48% of self-identified vegetarians aged one year and older reported eating some meat, poultry, or seafood during dietary recall days. 43 Dietary recall data of self-identified vegetarians can be found here. As can be seen in the data, many of the self-identified vegetarians reported consuming multiple foods that include meat.

Dietary recall data of self-identified vegetarians can be found here. As can be seen in the data, many of the self-identified vegetarians reported consuming multiple foods that include meat. Out of 1,274 respondents who self-identified as vegetarians in FooDS surveys between June 2013 and May 2015, 733 (57.5%) chose at least one product with meat in hypothetical choice experiment questions, where individuals had to evaluate several different meat and non-meat options at different prices and indicate the one product they are most likely to purchase.44

There are multiple possible explanations for this phenomenon.45 It is possible that the percentage of people who call themselves vegetarians has been increasing but the percentage of people who actually do not eat meat has not. Consequently, we have to look at the surveys that ask people about their actual consumption.

Dietary vegans

I found few surveys that asked respondents whether they consider themselves vegans:

The results of some of the more recent surveys seem to be unrealistically high. This could be due to high margins of error. It could also be due to people not knowing what the word vegan means. Some evidence for this comes from the Newport (2012) poll in which 7% of the respondents chose the “no opinion” option when asked if they were vegan. What is more, most of the respondents who considered themselves vegans did not consider themselves vegetarians. The 2002 TIME magazine poll asked the question about veganism only to the respondents who claimed that they are vegetarians. Consequently, the results of these two polls should not be compared.

Surveys About Both Self-Identity and Consumption

Vegetarians

I’ve found only six surveys that asked about both self-identity and food consumption:

Study Year Sample size % Self-identified vegetarians who did not indicate that they consume meat Surveying method Minimal age of respondents in years Continuing Survey of Food Intakes by Individuals (CSFII)47 1994–1996, 1998 9,854 0.9% Face-to-face, combined with a health examination, follow-up via telephone48 20 Faunalytics (2007) 2005 3,200 1% Online survey 18 NHANES 2007–2008 4,897 0.75% Face-to-face, combined with a health examination, follow-up via telephone 18 NHANES 2009–2010 5,284 1.01% 18 Faunalytics (2014) 2014 11,429 1.9% Online survey 17 Asher (2017) 2016 26,466 1.1% Online survey 18

However, not all of these studies are directly comparable because they all qualified vegetarians in different ways:

As described in the previous section, the CSFII survey analysis disqualified all the self-identified vegetarians who had eaten at least 10g of meat in one or both 24-hour periods for which data had been collected.

Faunalytics (2007) asked respondents how often they eat meat. Of the 40 respondents who indicated that they “never” eat meat, 80% described themselves as vegetarian, 5% did not, 10% said they were unsure, and another 5% wrote in some other response. Only those who described themselves as vegetarians were categorized as such.

Similarly to CSFII, my NHANES 2007–2010 survey analysis disqualified all the self-identified vegetarians who had eaten meat in one or both 24-hour periods for which data had been collected.

Faunalytics (2014) first asked, “Which foods/beverages do you currently consume?” Respondents who did not indicate that they eat beef, pork, chicken, turkey, fish, seafood, or other meats (but eat either eggs or dairy) were then asked whether they currently eat a vegetarian diet (defined as “one with no meat, i.e., without beef, pork, chicken, turkey, fish/seafood, etc.”). Those who answered “No” were classified as non-vegetarians. Similarly, respondents who did not indicate that they eat any animal products but answered “No” when asked whether they eat a vegan diet were classified as neither vegans nor vegetarians.49 Note that out of these studies Faunalytics is the only one to ask about a vegan self-identity. Full details can be found in the survey instrument.

[ALL] 1. Which foods/beverages do you currently consume? Check any that apply. ▢ Fruit (apples, bananas, oranges, canned fruit, dried fruit, etc.)

(apples, bananas, oranges, canned fruit, dried fruit, etc.) ▢ Caffeinated drinks (coffee, tea, lattes, energy drinks, chocolate drinks, etc.)

(coffee, tea, lattes, energy drinks, chocolate drinks, etc.) ▢ Vegetables (carrots, mushrooms, potatoes, onions, peas, etc.)

(carrots, mushrooms, potatoes, onions, peas, etc.) ▢ Turkey (turkey dinner, turkey sandwich, turkey gravy, turkey burger, etc.)

(turkey dinner, turkey sandwich, turkey gravy, turkey burger, etc.) ▢ Chicken (wings, nuggets, chicken noodle soup, chicken salad, chicken sandwich, etc.)

(wings, nuggets, chicken noodle soup, chicken salad, chicken sandwich, etc.) ▢ Nuts (almonds, cashews, walnuts, peanut butter, pecans, etc.)

(almonds, cashews, walnuts, peanut butter, pecans, etc.) ▢ Fish, not including seafood (salmon, tuna, fish sticks, fish & chips, haddock, etc.)

(salmon, tuna, fish sticks, fish & chips, haddock, etc.) ▢ Seafood (lobster, shrimp, scallops, oyster, crab, etc.)

(lobster, shrimp, scallops, oyster, crab, etc.) ▢ Sweets (cookies, cakes, pie, candies, squares, etc.)

(cookies, cakes, pie, candies, squares, etc.) ▢ Pork (bacon, ham, pork chops, spare ribs, ham sandwich, etc.)

(bacon, ham, pork chops, spare ribs, ham sandwich, etc.) ▢ Beef (hamburger, steak, roast beef, meatloaf, in stew/lasagna/spaghetti/pizza, etc.)

(hamburger, steak, roast beef, meatloaf, in stew/lasagna/spaghetti/pizza, etc.) ▢ Other meats (duck, lamb, rabbit, deer, goat, etc.)

(duck, lamb, rabbit, deer, goat, etc.) ▢ Soft drinks (cola, ginger ale, lemon-lime, root beer, etc.)

(cola, ginger ale, lemon-lime, root beer, etc.) ▢ Eggs (scrambled/boiled, omelet, egg sandwich, quiche, in baked goods/sauces, etc.)

(scrambled/boiled, omelet, egg sandwich, quiche, in baked goods/sauces, etc.) ▢ Dairy (cheese including on pizza/pasta, milk/chocolate milk, yogurt, ice cream, butter, etc.)

Asher (2017) used a similar approach to Faunalytics (2014) to determine the percentage of true vegetarians.50 It also first asked about consumption, then about self-identity, and only qualified the respondents who gave answers that were consistent with vegetarianism in both questions. However, the question about consumption was much stricter. Even the people who claimed to eat meat “1–11 times per YEAR or less frequently” were considered to be non-vegetarians. Full details can be found in the survey instrument.

How often do you usually consume the following foods? Answer based on your current diet. Think about all the meals and snacks you eat. Also think about everything you eat at home or outside the home. Please take your time and carefully consider each question individually. Never 1-11 times per YEAR or less frequently 1 time per MONTH 2-3 times per MONTH 1 time per WEEK 2-4 times per WEEK 5-6 times per WEEK 1 time per DAY 2 or more times per DAY Beef (hamburger, steak, roast beef, meatloaf, in stews/lasagna/pasta/pizza, etc.) Pork (bacon, ham, pork chops, spare ribs, bacon bits, etc.) Chicken (wings, nuggets, chicken breast, chicken sandwich, in soup, etc.) Turkey (turkey dinner, turkey sandwich, turkey burger, turkey bacon, in soup, etc.) Fish, not including shellfish (salmon, tuna, fish sticks, haddock, fish & chips, etc.) Shellfish (shrimp, lobster, scallops, oysters, crab, etc.) Other meats (duck, lamb/sheep, goat, bison, etc.)

A comparison between CSFII and NHANES surveys which used similar criteria suggests that the percentage of vegetarians has not changed much between the mid-1990s and the late 2000s.

Even though Faunalytics (2014) found a higher percentage of vegetarians than Asher (2017), it does not necessarily follow that the percentage of vegetarians decreased between 2017 and 2014 because Asher (2017) used a much stricter question about consumption. For example, people who eat meat 1–11 times per year or less frequently might have answered the question about consumption in the way that classifies them as vegetarians in Faunalytics (2014) but not in Asher (2017). What is more, the sample of Asher (2017) was census-balanced on non-interlocking quotas for age, gender, region, and race/ethnicity. Faunalytics (2014) was not census-balanced. Compared to the U.S. population, the sample of Faunalytics (2014) was significantly more educated and higher income, slightly more female, white, and older.51 Vegetarians also tend to be more educated, higher income, and female. However, they tend to be non-white and younger.52 Combined, these differences probably caused Faunalytics (2014) to overestimate the percentage of vegetarians.

If we exclude Faunalytics (2014) from the analysis, we can see that Asher (2017) found the highest percentage of vegetarians despite having arguably the most strict qualification. This weakly suggests that the percentage of strict vegetarians is increasing, albeit slowly. However, note that here we are comparing the results of online surveys and face-to-face interviews which, as discussed previously, is problematic.

We can also compare the results of the recent studies with Roper (1978) which found that only 0.55% of 2,000 respondents described themselves as strict vegetarians.53 It seems that the percentage of strict vegetarians is higher now.

Dietary vegans

I have found only four surveys that asked about both consumption and vegetarian or vegan self-identification:

Survey Year Sample size % Did not indicate consumption of animal products % Self-identified vegetarians or vegans who did not indicate consumption of animal products Question Surveying method CSFII54 1994–1996, 1998 12,634 0.34% 0.11% “Do you consider (Yourself/NAME) to be a vegetarian?” Face-to-face, combined with a health examination, follow-up via telephone NHANES55 2007–2008 4,897 0.25%–0.37% 0.03% “Do you consider yourself a vegetarian?” NHANES 2009–2010 5,284 0.13%–0.31% 0.20% Faunalytics (2014) 2014 11,429 1.7%56 0.47% “Do you currently eat a vegan diet (one with no animal products, i.e., without beef, pork, chicken/ turkey, fish/seafood, dairy, eggs, etc.)?” Online survey

Percentages for NHANES studies are based on our own analysis of NHANES dietary recall data. Faunalytics (2014) asked respondents which foods they currently consumed and then asked whether respondents currently eat a vegan diet, with a definition given. It is surprising that Faunalytics (2014) found the highest percentage of vegans despite arguably having the strictest qualification. However, Faunalytics (2014) is an online survey with no census-balancing which makes its estimates less reliable.

Polls About Consumption by Vegetarian Resource Group (VRG)

Adult polls

Vegetarian Resource Group (VRG) has conducted a number of polls that asked U.S. adults aged 18 and over about their food consumption but not about their self-identity.

A comparison between different VRG polls is problematic because they differed from each other by:

Surveying methods

The phrasing of the question 65

Census-balancing method It seems that surveys before 2006 were not census-balanced; surveys after 2006 were census-balanced using different criteria



There are also significant margins of error. What is more, in many cases the exact percentages of vegans and vegetarians were not publicized in the reports. Instead, phrases like “about one-third to one-half of the vegetarians appear to be vegans” were used. In the table and graph above, I assigned numeric values based on these phrases and marked inexact values with a star.

We can notice that the two earliest VRG surveys (VRG 1994 and VRG 1997) found the lowest percentage of vegetarians and vegans. However, these are also the only two surveys that conducted face-to-face interviews in the respondents’ homes rather than surveying the respondents via telephone or online. As observed in other studies, face-to-face surveys tend to find much lower percentages of vegans and vegetarians than online and telephone studies. Consequently, no firm conclusions about the trends can be drawn from this data.

Nevertheless, it is surprising that in all VRG polls since the year 2000 the percentage of vegetarians found was so much higher than in the surveys examined in the previous section.66 One key difference is that the studies in the previous section required self-identification. In Faunalytics (2014), 3.7% of respondents were classified as vegans or vegetarians based on the answers to the question about consumption, but almost half of them did not identify as vegans or vegetarians. Hence, in this case there is no difference to explain. However, out of 391 individuals who indicated that they eat a meat-free diet in Asher (2017), only 60 were disqualified because they did not self-identify as vegetarians. This only partly explains the difference between VRG 2016 and Asher (2017). Both studies surveyed those aged 18 or over, sourced the data during 2016, and employed census-balancing. Despite the similarities, VRG 2016 found that 3.3% of respondents were vegetarian while Asher’s (2017) finding was only 1.1%. The key difference may be the formulation of the question, which in the case of Asher (2017) was stricter.

Youth polls

Most of the surveys I analyzed so far only surveyed adults, although some did include youths. VRG also conducted some polls that surveyed only youths. Just like in adult polls, the questions were about which foods they never eat, and the exact phrasing of the question changed multiple times.

Year Sample size % Vegetarians % Vegans, except for possibly honey % Vegans Age range Surveying method 1995 1,023 2% 1% Unknown 8–17 Face-to-face 2000 1,240 2% 1% 6–17 Face-to-face 2005 1,264 3% 1% 8–18 Online 2010 1,258 3% 2% 1% 8–18 Online 2014 1,213 3% 1% Unknown 8–18 Online

There seems to have been a slight increase between 2000 and 2005, but this could be due to a change in survey method and age range.

Analysis of NHANES Dietary Recall Data

The National Health and Nutrition Examination Survey (NHANES) administers a 24-hour dietary recall in addition to medical and dental examinations, physiological measurements, and laboratory tests.67 Beginning in 2002, all participants were asked to complete a second 24-hour dietary recall interview which is collected by telephone approximately 3–10 days after the exam. The data from the 24-hour recalls is freely available online.

We analyzed 2003–2014 dietary recall data to determine the percentage of people who ate a vegetarian or vegan diet during the two 24-hour periods. This required categorizing over 10,000 foods into vegan, vegetarian, and non-vegetarian. It was ambiguous whether many of the foods contained meat or other animal products. As a result, some subjective decisions were made when classifying the items:

Because any dish can have a vegan alternative, pie, muffin, pizza, and some other foods that typically contain animal products were classified as vegan unless a specific animal product was mentioned as an ingredient.

Items that almost always include meat (for example, cheeseburger, hot dog, sausage, chili con carne) were categorized as vegan for the upper bound calculations but as non-vegetarian for lower bound calculation. 68

If a food description contained the words “milk” or “cheese” (without specifying the exact type of product) it was classified as vegan for the upper bound calculation but non-vegan for the lower bound calculation. 69

Foods that had the words “meat” or “seafood” in the description were categorized as non-vegetarian, even though in some cases it might have been a substitute.

Honey was classified as vegan.

In the tables below, the upper bound was calculated by applying a less strict classification, as explained in the text above. Here are the results for people aged 18 and over:

Years Sample size % Did not consume any meat (vegetarian) % Did not consume any animal products (vegan) 2003–2004 4,602 1.68%–1.99% 0.05%–0.28% 2005–2006 4,529 1.57%–1.78% 0.17%–0.37% 2007–2008 4,895 1.99%–2.12% 0.25%–0.37% 2009–2010 5,284 2.07%–2.46% 0.13%–0.31% 2011–2012 4,555 2.10%–2.26% 0.06%–0.38% 2013–2014 4,746 2.08%–2.41% 0.03%–0.31%

Similarly, here are the results for the people aged 8–18:

Years Sample size % Vegetarian % Vegan 2003–2004 2,085 1.45%–2.09% 0.00%–0.02% 2005–2006 2,098 2.21%–2.48% 0.67%–0.76% 2007–2008 1,371 1.92%–2.60% 0.43%–0.67% 2009–2010 1,482 3.08%–3.81% 0.00%–0.10% 2011–2012 1,475 3.20%–3.86% 0.03%–0.30% 2013–2014 1,460 1.76%–2.12% 0.04%–0.12%

Furthermore, many people we classified as vegetarians or vegans indicated that they ate finfish or shellfish in the last 30 days in another question. If we treat such people as non-vegetarians,70 numbers decrease significantly. Here are the results for people aged 18 and over:

Years Sample size % Vegetarian % Vegan 2003–2004 1.364 1.42%–1.50% 0.00%–0.17% 2005–2006 4.529 0.82%–0.93% 0.17%–0.31% 2007–2008 4.895 0.86%–0.89% 0.19%–0.22% 2009–2010 5.284 1.36%–1.45% 0.11%–0.24% 2011–2012 4.552 1.14%–1.19% 0.02%–0.12% 2013–2014 4.745 1.03%–1.16% 0.03%–0.21%

And here are the results for the people aged 8–18:

Years Sample size % Vegetarian % Vegan 2003–2004 242 0.80% 0.00% 2005–2006 2,098 1.85%–1.95% 0.67%–0.72% 2007–2008 1,371 1.20%–1.56% 0.35%–0.57% 2009–2010 1,482 2.19%–2.29% 0.00%–0.02% 2011–2012 1,475 1.95%–2.13% 0.03%–0.29% 2013–2014 1,458 1.41%–1.67% 0.04%–0.12%

In the years 2003–2004 most of the respondents were not asked the question about fish consumption. It is unclear how respondents who were asked the question were selected. Therefore, we excluded years 2003–2004 from Graphs 5 and 6.

Also note that some non-vegetarians might have just happened not to eat anything we classified as non-vegetarian during the two 24-hour periods. Out of the people we classified as vegetarians based on dietary recalls, only 41% self-identified as vegetarians in 2007–2010. Out of the people we classified as vegetarians based on dietary recalls and questions about fish consumption in the last 30 days, 56% self-identified as vegetarians.71

The most important takeaway from our NHANES data analysis is that the percentage of vegetarians and vegans seems to be much lower than other studies suggest. It is surprising that a larger percentage of people reported never consuming meat (or any animal products) in VRG studies than not consuming it during two 24-hour periods in NHANES studies. It is possible that the NHANES surveying format made respondents more honest because it asked for detailed dietary data and combined the survey with a health examination. What is more, some of the VRG polls were online. As discussed before, online surveys probably tend to overestimate the percentage of vegetarians and vegans. However, it is also possible that NHANES surveys underestimate vegetarianism rates.

The results also weakly suggest that between 2003 and 2014 the percentage of vegetarians was increasing. We cannot conclude much about trends of veganism because the number of vegans on our sample is very small.

Appendix: Surveys That Were Not Used

I did not include some of the surveys that I found mentioned online for various reasons. I list some of the more notable such surveys here:

The 1976–1980 National Health and Nutrition Examination Survey surveyed 20,322 people. It included a question “Are you on a special diet?” There were 2,110 respondents who answered positively. These were then asked “What kind of diet is it?” 51 respondents answered “yes” to “Vegetarian with animal By-Products?” and 12 respondents answered “yes” to “Vegetarian without animal By-Products?” This could be interpreted as suggesting that there were 0.31% self-identified vegetarians and 0.06% self-identified vegans in the survey sample. However, many of the vegetarians might have selected “No” when asked “Are you on a special diet?” This could explain why the percentages in this study are so much lower than in 1977–1978 Nationwide Food Consumption Survey in which 1.2% of respondents self-identified as vegetarians. I decided that due to different structures it would be unfair to compare this survey with the surveys that asked about vegetarianism without any qualifying questions.

After describing Yankelovich, Clancy, & Shulman, which found 7% of Americans to be vegetarian, the October, 1992 issue of Vegetarian Times magazine mentioned that “a survey conducted by Bruskin Goldring Research, another market research firm, came up with an almost identical figure.” However, I haven’t managed to find any more information about this survey. Both of these surveys indicate that the number of self-identified vegetarians was higher in 1992 than it is now—which contradicts the trend that we see when looking at the other studies.

magazine mentioned that “a survey conducted by Bruskin Goldring Research, another market research firm, came up with an almost identical figure.” However, I haven’t managed to find any more information about this survey. Both of these surveys indicate that the number of self-identified vegetarians was higher in 1992 than it is now—which contradicts the trend that we see when looking at the other studies. In Chapter 1 of a 2002 book called Vegetarianism: Movement or Moment? by Donna Maurer there is the following text: “although vegetarianism’s popularity has waxed and waned—with its peaks occurring in the mid-1800s and in the 1960s and early 1970s—it has held a small but consistent following in the United States and Canada since the 1820s.” However, no evidence for the claim is provided. In the chapter “How Many Vegetarians Are There?” the book lists some surveys on the topic. Some of them are not included in my analysis, either because I couldn’t verify them, or because the surveyed population was not nationally representative. 72

by Donna Maurer there is the following text: “although vegetarianism’s popularity has waxed and waned—with its peaks occurring in the mid-1800s and in the 1960s and early 1970s—it has held a small but consistent following in the United States and Canada since the 1820s.” However, no evidence for the claim is provided. In the chapter “How Many Vegetarians Are There?” the book lists some surveys on the topic. Some of them are not included in my analysis, either because I couldn’t verify them, or because the surveyed population was not nationally representative. A 2008 study by Vegetarian Times surveyed 5,050 respondents, a statistically representative sample of the total U.S. population. According to the study results, approximately 3.2% of U.S. adults “follow a vegetarian-based diet” and approximately 0.5% are vegans. However, they did not publicize the survey questions, so it is unclear whether they asked about self-identity, consumption, or both.

surveyed 5,050 respondents, a statistically representative sample of the total U.S. population. According to the study results, approximately 3.2% of U.S. adults “follow a vegetarian-based diet” and approximately 0.5% are vegans. However, they did not publicize the survey questions, so it is unclear whether they asked about self-identity, consumption, or both. There are surveys that are clearly not nationally representative. This include the ones that surveyed only a specific subpopulation (e.g., college students, people living in one city, women, etc.). Most notably I excluded Macdonald et al. (2016) from the analysis because it simply recruited American participants with high approval rates from Amazon Mechanical Turk without trying to make the survey nationally representative.

I warmly thank Harry Burdon for analysing NHANES data. I also warmly thank ACE staff, Jo Anderson, and Annie Alexander-Barnes for copyediting and providing important suggestions and comments on this post.

Year,Respondents,Self-identified vegetarians (% weighted) May-13,"1,000",4.7% Jun-13,"1,003",3.9% Jul-13,"1,016",5.0% Aug-13,"1,022",4.1% Sep-13,"1,003",4.5% Oct-13,"1,075",5.7% Nov-13,"1,021",3.6% Dec-13,"1,017",4.0% Jan-14,"1,004",3.8% Feb-14,"1,022",4.4% Mar-14,"1,039",3.3% Apr-14,"1,016",3.8% May-14,"1,019",4.4% Jun-14,"1,032",4.1% Jul-14,"1,017",3.4% Aug-14,"1,012",3.9% Sep-14,"1,045",5.5% Oct-14,"1,016",4.7% Nov-14,"1,010",4.1% Dec-14,"1,014",4.3% Jan-15,"1,016",5.6% Feb-15,"1,001",6.5% Mar-15,"1,040",5.4% Apr-15,"1,012",4.8% May-15,"1,064",5.9% Jun-15,"1,034",5.2% Jul-15,"1,063",6.4% Aug-15,"1,022",5.9% Sep-15,"1,003",4.3% Oct-15,"1,016",4.2% Nov-15,"1,009",5.4% Dec-15,"1,002",5.8% Jan-16,"1,000",3.8% Feb-16,"1,085",5.1% Mar-16,"1,030",5.4% Apr-16,"1,002",7.9% May-16,"1,023",5.6% Jun-16,"1,035",7.63% Jul-16,"1,003",7.61% Aug-16,"1,058",5.55% Sep-16,"1,061",6.93% Oct-16,"1,036",7.74% Nov-16,"1,005",5.67% Dec-16,"1,132",6.60% Jan-17,"1,059",7.29% Feb-17,"1,142",5.19% Mar-17,"1,018",6.96% Apr-17,"1,001",6.70% May-17,"1,030",3.53% Jun-17,"1,049",4.45% Jul-17,"1,025",4.13% Aug-17,"1,026",6.25% Sep-17,"1,125",5.02% Oct-17,1050,5.04% Nov-17,1044,3.60% Dec-17,1022,6.62% Jan-18,1017,5.45% Feb-18,1025,6.74% Mar-18,1007,5.74% Apr-18,"1,000",6.03% May-18,1000,8.80%

year,% Vegetarians (including vegans),"" 1994,0.65%,0 1997,1.00%,0 2000,2.50%,0 2003,2.80%,0 2006,2.30%,0 2009,3.40%,0 2011,5.00%,0 2012,4.00%,0 2015,3.40%,0 2016,3.30%,0

years,vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound),TRENDLINES ->,vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound) 2003-2004,1.99%,1.68%,0.28%,0.05%,0.01893365905,0.01651802714,0.003273727619,0.00154144619 2005-2006,1.78%,1.57%,0.37%,0.17%,0.02004322476,0.01756616629,0.003307471905,0.001387393048 2007-2008,2.12%,1.99%,0.37%,0.25%,0.02115279048,0.01861430543,0.00334121619,0.001233339905 2009-2010,2.46%,2.07%,0.31%,0.13%,0.02226235619,0.01966244457,0.003374960476,0.001079286762 2011-2012,2.26%,2.10%,0.38%,0.06%,0.0233719219,0.02071058371,0.003408704762,0.000925233619 2013-2014,2.41%,2.08%,0.31%,0.03%,0.02448148762,0.02175872286,0.003442449048,0.0007711804762

years,vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound),vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound) 2003-2004,2.09%,1.45%,0.02%,0.00%,0.02435027429,0.01864476048,0.004302108571,0.003456622381 2005-2006,2.48%,2.21%,0.76%,0.67%,0.02592314457,0.02026515362,0.003889137143,0.002846912095 2007-2008,2.60%,1.92%,0.67%,0.43%,0.02749601486,0.02188554676,0.003476165714,0.00223720181 2009-2010,3.81%,3.08%,0.10%,0.00%,0.02906888514,0.0235059399,0.003063194286,0.001627491524 2011-2012,3.86%,3.20%,0.30%,0.03%,0.03064175543,0.02512633305,0.002650222857,0.001017781238 2013-2014,2.12%,1.76%,0.12%,0.04%,0.03221462571,0.02674672619,0.002237251429,0.0004080709524

years,vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound),vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound) 2005-2006,0.93%,0.82%,0.31%,0.17%,0.00972,0.00902,0.0028,0.00194 2007-2008,0.89%,0.86%,0.22%,0.19%,0.01048,0.00972,0.0025,0.00149 2009-2010,1.45%,1.36%,0.24%,0.11%,0.01124,0.01042,0.0022,0.00104 2011-2012,1.19%,1.14%,0.12%,0.02%,0.012,0.01112,0.0019,0.00059 2013-2014,1.16%,1.03%,0.21%,0.03%,0.01276,0.01182,0.0016,0.00014

years,vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound),vegetarians (upper bound),vegetarians (lower bound),vegans (upper bound),vegans (lower bound) 2005-2006,1.95%,1.85%,0.72%,0.67%,0.01914254,0.017474554,0.006377878,0.005319184 2007-2008,1.56%,1.20%,0.57%,0.35%,0.019171654,0.017332786,0.004904185,0.003745838 2009-2010,2.29%,2.19%,0.02%,0.00%,0.019200768,0.017191018,0.003430492,0.002172492 2011-2012,2.13%,1.95%,0.29%,0.03%,0.019229882,0.01704925,0.001956799,0.000599146 2013-2014,1.67%,1.41%,0.12%,0.04%,0.019258996,0.016907482,0.000483106,-0.0009742