Why This is Important
Not all registered voters vote in a primary election, though in North Carolina they can. In some states, only those affiliated with a party are able to vote for their party's candidates. In North Carolina any registered voter can cast a ballot in a primary.
Typically, many fewer individuals vote in primary elections, and those that do are expressing additional interest in local or partisan issues and policies. As an indicator of engagement this measurement is both a reflection of above-average voting activity, and a reflection of deeper engagement in the political process and its institutions.
About the Data
For 2012, the data included in this measure reflect active voters only. The Board of Elections codes voters 'inactive' when their most recent address may be inaccurate. Due to the potentially inaccurate addresses of inactive voters, this spatial analysis relies only on the active voters. As of January 2014, there were 176,148 active voters out of a total 200,885 registered in Durham County.
In order to have data which is comparable with commonly-reported voter participation statistics, metric values are scaled so that the total number of registered voters and total number of ballots cast line up with the values reported by the Durham County Board of Elections. So, for example, for the 2012 Presidential General Election, we multiplied our calculated value for number of ballots cast per blockgroup (which only included geocodable addresses) by 1.073 to account for the fact that the Board of Elections final count of ballots cast was 147,497 but the Compass geocoded values only accounted for 137,455 ballots, and we similarly scaled our values for registered voters by 1.21 to account for the fact that we only had valid geocodes of 175,721 voters, where the Board of Elections had 212,654 voters registered.
Sources: Durham County Board of Elections and Redistricting Data Hub