Voter Registration and Turnout

Election Data
With the Super Tuesday primaries this past Tuesday, I decided to take a brief look at whatever voting data I could find. I found the Election Assistance Commission web site with data from several past years' elections. I grabbed the 2002 registration and turnout data by state. I'd love to get some more recent data. If you know of a source, please email me or leave a comment.

My initial hypothesis was that registration and turnout should have a pretty strong correlation since, after all, you can't vote if you're not registered. On the other hand, I know that there are some pretty strong voter registration drives with multiple venues for registering, while actual voting is quite controlled and limited in the number of locations where a person can vote. Registration can be highly influenced by outside factors (such as availability and ease of access) while voting itself often needs to be self-motivated.

Here's a plot of the % Register vs. % Turnout by state for the 2002 election:

The coefficient of correlation is 0.382.

Breakdown by Region
Then I thought that perhaps the correlation may be culturally influenced. Could it be that in the northeast states, registration is more closely correlated with voter turnout while in another region the relationship is not as close?

I used the 4 major regions of the US (Northeast, Midwest, South and West) as defined by the US Census Regions and Divisions, and used Minitab to create the plot below:

The regions are:
Northeast 1
Midwest 2
South 3
West 4

I hope to compare the basic descriptive statistics for each region as well as the correlations soon. I do notice some clustering of the data points on cursory inspection.

[Edit] Correlation coefficients by region are:
Northeast: 0.676
Midwest: -0.338
South: 0.063
West: 0.665

How interesting! In the Northeast and West regions, voter turnout is relatively well correlated with registration, while in the South there is little correlation and in the Midwest it's negative! I think a logical next step is to normalize for the total population of each region.

All just food for thought while I wait to get back into the coursework tonight...