I, along with approximately one third of eligible California voters, decided to vote yesterday. I am not particularly interested in a high voter turnout. I believe people who are pressured to vote because of "get out the vote" campaigns only end up diluting researched opinions with random noise.
One thing I do hear a lot is that republicans are more likely to come out and vote than democrats, especially in mid-term elections. So I decided to check this. I used the California County Reporting Status and the California Report of Voter Registration (it's a little out of date, but should be fine for this quick study) to figure out if Republicans are more likely to vote in mid-term elections than Democrats. In the figure below I plotted the voter turnout percentage against the percentage of registered democrats (blue dot) and percentage of registered republicans (red dot). I also drew a trendline showing the relationship between the percentage turnout by county and the percentage registration in each of those two parties.
Although there is a lot of scatter, if we assume that the only differences between the democrats and republicans in each county are correlated with their political preferences, then it appears that it is true that registered democrats are less likely to come out to vote than republicans during mid-term elections in California.