Gas tax and per capital VMT and gasoline consumption, visualized multiple ways

I’ve been wondering about California’s gas tax increase, and where that puts us in terms of other states. The American Petroleum Institute has a nice way of calculating the effective tax in each state, plus the federal tax, but they don’t have the data for download. I am bloody-minded enough to just type it a spreadsheet from their report here. I got per capita VMT and per capita gasoline consumption data from RITA.

I’m looking at data for states here.

First off, just some distributions of the data: gas tax levels, gallons/person, and vehicle miles of travel / person.


Irritating bi-modality there I get rid of by binning differently, but that wouldn’t be honest, now would it?



This here 3-d scatterplot is ugly because of the overplotting, but you can really see the states that are outliers in all three variables:


Here’s a scatterplot matrix where you see how we are not choosing fuel efficiency (e.g., the trend between gas consumed and VMT per person. I logged all the variables to try to pull those outliers, but it only worked so much. I think there’s a slight negative relationship between tax and VMT. Again, fleet efficiency is a variable we are not seeing here, along with a bunch of other factors (consumer demographics, retail gas prices) so we wouldn’t expect to see straightforward relationships.


and some rankings, since you know you want ’em, even though they aren’t very informative–there really isn’t much variation save for those outliers. Here we can see the effects of urbanization. DC is small and entirely urbanized, for all practical purposes.

VMT Person