Nick V. Flor (@ProfessorF)

When pollsters publish their latest polls and they don’t agree with reality as you know it, you owe it to yourself to “Unskew the Polls!” — discover the truth about who’s really ahead. But how exactly do you unskew the polls?

Here’s one way to unskew the polls, but a word of caution: You may not like what you find — I sure wasn’t.

An example of a questionable poll

First, let’s look at a poll that doesn’t square with reality: the latest Fox News Poll that shows Hillary with a +5 lead over Trump among likely voters:

Hillary Leads Trump +5 (49–44=5)

“Baloney! You scream. I’ve been to a Trump rally”:

Trump Rally in Ohio (courtesy @realtacoking25)

“There’s no way she can be ahead. Something fishy is going on.” So you scrutinize the polling methodology, and you discover that the polls oversampled Democrats by +4:

An Example of Oversampling Democrats by +4 (42–38=4)

You triumphantly go on Twitter and proclaim that the only reason Hillary’s ahead is because they oversampled Democrats. Like this guy:

An Angry Tweet Calling for Unskewing the Polls

Now it’s perfectly fine to post an opinion like that. But it just begs the question: “Is Trump actually ahead? And if so, by how much?” To answer this question you have to unskew the polls.

How to unskew the polls

Step 1. Find the True Proportion of D’s, R’s, and I’s

Finding the True Proportion™ of Democrats, Republicans, and Independents is the key to unskewing. If there aren’t +4 (4%) more Democrats than Republicans, then what is the true percentage?

One way to find out is to go to Gallup. They conduct a weekly poll of voter identification:

Gallup Weekly Poll on Party Affiliation

I’ve only printed two rows of this poll, but as you can see party identification changes weekly. Ignoring “leaners”, on Sept 7–11, 29% identified as Republicans and 31% identified as Democrats→+2 Democrats.

But on Sept 14–18, 27% identified as Republicans and 32% as Democrats → +5 Democrats, in just a week!

The other thing to note is that a lot of people identify as independent: 38% on Sep 7–11, and 40% in Sep 14–18. So if anything, most polls don’t oversample Democrats, they undersample Independents. This sounds like a good thing if you’re a Republican because Independents are leaning Trump significantly.

But continuing on, let’s go with the latest proportions:

27% Republicans (PR)

40% Independents (PI)

32% Democrats (PD)

I labeled these numbers in parentheses for future reference. These labels are arbitrary. For example, I chose PR because it’s easy to remember as Percentage Republicans.

Step 2. Find the voting percentages of D’s, R’s, & I’s

You’re almost ready to unskew.

You need to find what percentage of Democrats will vote Hillary, and what percentage will vote Trump. Similarly you need to find what percentage of Republicans will vote Trump and what percentage (are traitors! and) will vote Hillary. And, finally, you guessed it, find out what percentage of Independents will vote Trump and what percentage will vote Hillary.

That sounds like a lot of data to collect but fortunately most polls have a single question that summarizes all this data:

How the various political parties will vote

Here are all the numbers we need, based on the table:

92% of Democrats will vote Hillary (DvD: Democrats that vote Democrat)

4% of Democrats will vote Trump (DvR)

87% of Republicans will vote Trump (RvR)

9% of Republicans (traitors) will vote Hillary (RvD)

45% of Independents will vote Trump (IvR)

34% of Independents will vote Hillary (IvD)

Now we can finally unskew the polls.

Step 3. Unskew the polls using the data in Steps 1&2

The formula is simple:

Democrat=PD×DvD + PR×RvD + PI×IvD

Republican=PR×RvR + PD×DvR + PI×IvR

Now let’s plug in the candidates and the numbers:

Hillary=32%×92%+ 27%×9%+ 40%×34%=45.47%

Trump=27%×87%+ 32%×4%+ 40%×45%=42.77%

What the heck?!? Even when we unskew the polls, Hillary is up by 2.7% (45.47–42.7=2.7).

Sadly for Republicans, the numbers don’t lie, and we have to accept the fact that Hillary may indeed be ahead of Trump despite the oversampling of Democrats.

Hope for Republicans

It all depends on the true proportion of Democrats, Republicans, and Independents. If we use a different set of proportions, we can get a more favorable result. Take Gallup’s July 13–17 proportions:

On July 13–17, the proportion of Republicans, Independents, and Democrats was 28%, 42%, 28% (last row)

If you plug those values in, you get:

Hillary=28%×92%+ 28%×9%+ 42%×34%=42.56%

Trump=28%×87%+ 28%×4%+ 42%×45%=44.38%

In this case, Trump wins by +1.82

It all depends on what are the true proportions. The bad news for Republicans is that historically there have always been slightly more Democrats than Republicans.

The good news: Republicans are voting more than Democrats in 2016. Given the voting percentages in Step 2, that predicts a victory for Trump.

Turnout will determine the election.