Full methodology: 2018 Early voting analysis

Early voting changes hit NC rural voters hardest, analysis shows. But will it matter in 2018?

Early, or so-called "one-stop," voting locations allow eligible citizens in the county to vote at any location, instead of voting at a specific precinct.

Republican lawmakers said the changes were important to ensure consistency within counties and cut down on voter confusion. But opponents of the measure said it reduces county flexibility and worried that it could cut voting opportunities for those that couldn't afford to keep sites open for 12 hours straight.

In practice, the number of hours available statewide to vote early at one-stop locations nearly doubled since 2014 – from 25,887 to 49,696. Total early voting hours increased in all but six counties: Henderson, Bladen, Stanly, Polk and McDowell and Halifax.

Yet a question remains: Did the change in early voting locations disproportionately impact any group of voters in particular?

We sought to answer the question using data on more than 7 million registered voters.

WRAL News used the following publicly available data from the State Board of Elections and Ethics Enforcement:

Latitude and longitude coordinates for 2018 early voting locations were obtained from the State Board of Elections and Ethics Enforcement's lookup tool by using a Python script.

In 30 North Carolina counties, there were no changes in early voting locations between 2014 and 2018, so these counties were omitted from the analysis. This left 580 sites for the two midterm elections. Voters in these counties were also omitted from this analysis, leaving 6,433,969 active and inactive voters, both of which are eligible to cast ballots, according to state elections officials.

While some early voting locations may have been relocated due to the impact of hurricanes Florence or Michael, this analysis considered only the original early voting locations approved by local elections board and the state board.

Latitude and longitude coordinates were then matched to active and inactive registered voters on addresses, city, county and ZIP using MySQL database software. The query failed to match the addresses of 145,645 voters, a 97.7 percent match rate.

Open Route Service limits queries through its API to 10 shapefiles at a time. The service also limits total API queries to 2,500 a day.

Due to these limitations, the Python script runs queries for each site four times to produce a geojson feature collection with shapefiles at half-mile intervals from 0.5 to 20, with each polygon describing a driving distance range.

For example, a point that appears in the isochrone with a mile value of 5, but not in an isochrone with a mile value of 4.5, is within 4.5 and 5 miles from the early voting location.

We then used database software to calculate the change in distance from the closest voting location in 2014 and the closest early voting location in 2018 for every active and inactive voter.

Because the driving distances were limited to 20 miles from each voting location, 62,325 voters could not be matched with either a 2014 or 2018 isochrone because they were outside the 20-mile range. This amounts to less than 1 percent of the registered voters in the study for which the difference in driving distance could not be calculated.

Using these values, we can calculate average, median, maximum and standard deviation values for each of the following subgroup types defined in the voter registration data:

We can also calculate average, median, maximum and standard deviation values for two types of county geographic designations: