Fast food has been a staple of American culture ever since the postwar era. Up there with apple pie and baseball, burgers and fries from the drive-thru have become quintessentially American both at home and abroad as brands like McDonald's (NYSE:MCD), Yum! Brands' (NYSE: YUM) KFC, and Restaurant Brands International's (NYSE: QSR) Burger King have opened thousands of locations around the globe.

Despite the trend toward healthy eating and organic foods, fast food remains popular. Its low prices help ensure a steady flow of traffic, especially from those who have struggled to get back on their feet following the recession. After all, it's hard to beat $5 for a tasty, calorie-laden meal.

Let's take a look at some figures that show how pervasive the fast food industry is today.

1. 50 million

Fast-food restaurants serve 50 million people in the U.S. each day. That's nearly 1 out of every 6 Americans.

2. 160,000

There are 160,000 fast food restaurants in the country, or about 1 for every 2,000 Americans. Of those, more than 14,000 are McDonald's and more than 25,000 are Subways. If 50 million people eat at a fast food chain every day then the average restaurant serves about 300 people a day.

3. $110 billion

Annual revenue in the U.S. from fast food is $110 billion, or about one-seventh the total revenue from restaurants and bars in the country. From that, about $35 billion comes from McDonald's, which does more than $80 billion in systemwide sales around the world.

4. 28%

More than a quarter of Americans, or 28%, eat at a fast food restaurant at least once a week, meaning fast food is a regular part of many American's diet -- the drive-thru has made it an easy option for commuting, and it's also a opular choice for workday lunches. 3% say they eat fast food every day. By contrast, 4% of Americans say they never eat fast food.

5. 3.6 million

About 3.6 million people, or 2% of the American workforce, is employed by fast-food restaurants. It is a high-labor industry and also notorious for paying low wages. Average wages for fast-food workers are about $9/hour. Still, fast food is perceived by most Americans as unhealthy.



6. 836

The average fast food meal has 836 calories. In recent years, health concerns have prompted fast-food chains to adapt their offerings with healthier meals like salad and more humane treatment of animals; many chains have promised to switch to cage-free eggs, and McDonald's said it would stop serving chicken treated with human antibiotics.

7. $550 billion

With $550 billion in annual global sales, fast food is as popular in much of the rest of the world as it is in the U.S. Yum! Brands (NYSE:YUM) KFC has found a great deal of success in China, and many American fast food brands are popular in Europe, Latin America, and Asia.

8. 30%

About 30% of fast food restaurants serve burgers and fries. Other popular concepts include sandwiches, chicken, Mexican, and pizza.

9. 50 billion

In addition to burgers, fries, and other usually greasy food, soda is a significant component of fast-food sales. Last year, restaurants sold 50 billion servings of soda, but that number was down 4% from the previous year. The declining popularity of soda could put pressure on restaurants, as those beverage are the highest-margin items they sell.

Overall restaurant sales have outpaced general retail sales for the past several years, and that pattern should continue barring a potential recession. Results at fast-food restaurants have been mixed, but the category has been stronger than many have expected considering the larger trends in food.

Some fast-food chains have learned from their fast-casual rivals, adapting to a more modern decor and using less processed ingredients. Looking ahead, the industry should continue to grow at a modest pace, but for investors, most of these stocks look fully valued.