Do minorities get out the vote more when they have a candidate of their same race or ethnicity? Is voter turnout for people of color greater in areas where they represent a larger part of the population? Is there a mathematical formula to pinpoint racial voting patterns?

These are some of the questions probed in a new study by Bernard L. Fraga of Indiana University. In "Candidates or Districts? Reevaluating the Role of Race in Voter Turnout," Fraga uses data from 3,000 recent congressional primary and general elections to analyze minority voting patterns in the U.S. The conventional theory has been that minority voters are mobilized by co-ethnic candidates. The study discovered otherwise:

"I find that minority turnout is not higher in districts with minority candidates, after accounting for the relative size of the ethnic group within a district," Fraga wrote. "Instead, Black and Latino citizens are more likely to vote in both primary and general elections as their share of the population increases, regardless of candidate race."

In at elections from 2006, 2008 and 2010, larger voter turnout among minority groups was not predicated solely upon having a candidate of the same background.

Rather, turnout is often higher for minority voters who live in a congressional district where their racial or ethnic group represents the majority of the citizen voting-age population (CVAP). This was especially true for Black and Hispanic voters. In short, the majority demographic in any district tended to vote most.

Variable A: There is no Black candidate on the ballot. In this case, districts where Black people make up 10 percent of the voting-age population, the general-election turnout for Black voters is roughly 40 percent. The turnout is notably higher (49.3 percent) in a district where black people make up 50 percent of the voting-age population.

The same goes for Latino voters. Without a Latino on the ballot, the turnout is 6.4 percentage points higher in Latino-majority (40 percent or more voting-age population) districts, compared to Latino-minority districts (10 percent or less voting-age population).

In terms of policy, Fraga suggested that state legislators need "a new metric to judge what is fair when crafting district boundaries." He noted that, as minority populations rise, the voting districts will become more diverse. No amount of gerrymandering can prevent that.