Want to find Donald Trump voters in Pennsylvania? Look for lots of motorcycles

If you want to find supporters of President Donald Trump, go to places with lots of motorcycles.

That's what we found when we analyzed motorcycle registration and election data from the state.

Counties with a higher number of registered motorcycles were more likely to have supported Trump in 2016, when you adjust for population size.

Nearly all of the Pennsylvania counties that Trump won in 2016 had a higher rate of registered motorcycles than the state average.

Of course, correlation does not equal causation. (For instance, as "The Simpsons" taught some of us, just because you are holding a rock and there are no tigers nearby doesn't mean it's the rock that is keeping the tigers away.)

But let's look at what we found.

Consider Somerset County, about 70 miles southeast of Pittsburgh.

It ranks third in the state for the number of registered motorcycles per capita. For every 100 people in the county, there are nearly six registered motorcycles.

And in the November 2016 election, nearly 77 percent of voters there supported Trump, a Republican real estate mogul and former reality TV star.

The reverse is often true, as well.

More: Harley-Davidson motorcycle plant consolidation to bring hundreds of jobs to York County

The places with the lowest number of registered motorcycles per capita were: Philadelphia; Delaware and Montgomery counties, both in the Philly suburbs; and Allegheny County, home to Pittsburgh.

Those were also the four places where Trump got the lowest percentage of the vote in 2016.

G. Terry Madonna, a pollster and political science professor at Franklin & Marshall College in Lancaster, hadn't heard about a motorcycle/Trump connection before.

“I wonder who got the bicycle vote?" Madonna said. "I’m half-kidding, but not."

There's a lot that the correlation between Trump support and motorcycle registration doesn't tell you. For one, it doesn't tell you whether motorcycle riders themselves were more likely to vote for Trump.

See this video of how Trump won Pennsylvania in 2016 (story continues below):

But Madonna said it's fair to say this: Rural and small towns in Pennsylvania carried the state for Trump. And, it turns out, people in those places are more likely to have motorcycles.

York County is among those places, and it's home to a Harley-Davidson plant — one that is going to be adding hundreds more jobs as part of a consolidation plan the company recently announced. And the county's annual Bike Night is an example of the pretty big motorcycle culture here.

Here is an interactive map of whether counties have an above average number of registered motorcycles, per capita. Green counties have above average motorcycle registration. Purple ones don't.

York County ranks 20th out of 67 counties for the number of registered motorcycles per capita. As for Trump support, the county ranks 44th in the state, percentage-wise. He got more than 62 percent of the vote in York County.

Read: Harley-Davidson motorcycle plant consolidation to bring hundreds of jobs to York County

Here's a look at some other counties in the southcentral Pennsylvania region:

Adams County: Ranks 11th for motorcycle registration and 35th for Trump support.

Ranks 11th for motorcycle registration and 35th for Trump support. Cumberland County: Ranks 56th for motorcycle registration and 53rd for Trump support.

Ranks 56th for motorcycle registration and 53rd for Trump support. Dauphin County: Ranks 58th for motorcycle registration and 60th for Trump support. (Dauphin County is the only southcentral Pennsylvania county Trump lost).

Ranks 58th for motorcycle registration and 60th for Trump support. (Dauphin County is the only southcentral Pennsylvania county Trump lost). Franklin County: Ranks 38th for motorcycle registration and 18th for Trump support.

Ranks 38th for motorcycle registration and 18th for Trump support. Lancaster County: Ranks 49th for motorcycle registration and 52nd for Trump support.

Ranks 49th for motorcycle registration and 52nd for Trump support. Lebanon County: Ranks 24th for motorcycle registration and 37th for Trump support.

And after Trump took office, during his first address to a joint session of Congress in February 2017, he called Harley-Davidson "a great American company" and he talked about meeting with officials from the business.

"In fact, they proudly displayed five of their magnificent motorcycles, made in the USA, on the front lawn of the White House," Trump said. "And they wanted me to ride one and I said, 'No, thank you.'"

About the data: The registered motorcycle information comes from the Pennsylvania Department of Transportation. We used vehicles classified as regular motorcycles for our comparisons.

The election figures are from the Pennsylvania Department of State.

Why did we decide look at this data? We were looking at the impact of the 2003 law that made it legal for most riders in Pennsylvania to go without a helmet. We gathered a bunch of data, and then we noticed there might be a connection between Trump support and the number of registered motorcycles in counties. So we crunched some more numbers.