Who Will Win in 2016? Ask Someone from Connecticut

Minitab Blog Editor 25 August, 2015

Presidential Seal

There's more data available today than ever before, and with statistical software such as Minitab it only takes a couple of seconds to get some significant insights, whether it concerns how to make your business run better or national politics

For instance, if we look back at the last 9 presidential elections (1980 to 2012), there are some interesting correlations between the percent of state votes for Democrats/Republicans and the percent voting for Democrats/Republicans nationally.

The bar chart below shows how each state's percent Democratic vote count correlates with the percent national vote count. (Each state's votes were taken out of the national count before the correlation was calculated, so that a state like California didn't have a high correlation just because it has a large proportion of the national vote.)

individual state correlations with national popular vote

Connecticut had the highest correlation, and the fitted line plot below, which plots Connecticut's percent Democratic voting against the national percentage, shows just how closely correlated the state's percentages have been over the last nine presidential election cycles. 

Connecticut correlation

Other states, including Michigan and Ohio, had similarly high correlations. Keep in mind, however, that no matter how high these correlations are, correlation does not imply causation. If a candidate focused on Connecticut thinking their national percent would increase, they would be falling victim to flawed statistical thinking. In fact, that candidate's percent in other states would probably decrease, as opposed to increase, since they would be neglecting the other states.

West Virginia had the lowest correlation with the national voting percentages—so low, in fact, that its correlation was negative. 

West Virginia correlation

In years where West Virginia saw a high percentage of voters go Democratic, the national Democratic vote percent was low, and in years where West Virginia had a low Democratic vote percent, the Democratic vote percent was high at the national level. In general, southern states (South Carolina, Mississippi, Louisiana, Georgia, Arkansas, Tennessee, Kentucky, and Alabama) had low correlations with the national percentages. 

This data came from The University of California Santa Barbara website, http://www.presidency.ucsb.edu/elections.php, which has state-by-state historical voting data. As the 2016 election cycle gathers more steam, it will be very interesting to see what the data from a myriad of sources will be able to tell us.