The rapid growth of the country’s Hispanic population has added millions of voters in recent years. But new data from the Pew Hispanic Center show that Latinos are responsible for a smaller portion of the electorate than many might expect.

There are a couple of reasons for this.

One is a turnout rate that lags behind other cross sections of the electorate. Simply put, the percentage of eligible Hispanic voters who turn out is less than the percentage of eligible black and white voters who cast ballots. In 2008, roughly half of all eligible Hispanic voters cast ballots – a number notably lower than the 65 percent of eligible black voters and 66 percent of eligible white voters who did so.

As the Hispanic population grows, so does the number of eligible Hispanic voters, as the chart below shows. This year, nearly 24 million Hispanics are eligible to vote – about 4 million more than in 2008. The question is what turnout will look like in November.

Another reason Hispanic voter participation isn't higher is eligibility. The majority of the country’s Hispanic population (55 percent) is simply not eligible to vote. This stands in contrast to other ethnic groups. As the Pew data show, about one in five whites is ineligible to vote, while about a third of blacks and just under half of Asians aren't eligible to cast ballots.

Why are so many Hispanics ineligible to vote? The Pew report shows that for one thing, the Hispanic population is relatively younger, so many Latinos don't meet the 18-year-old age requirement. Secondly, there are many Hispanics living in the country who are not U.S. citizens.

All of this isn’t to say that the growing Hispanic population isn't impacting the electorate in a major way. It is – just at a more gradual rate than many people might think. And as the population ages, its impact will be more palpable at the ballot box.

Take Texas, which Census data show is now a majority-minority state, spurred in part by Hispanic population growth. It’s also a very Republican state. But as the number of Hispanic voters (who typically favor Democrats) continues to grow, the Republican stronghold could become more Democratic in coming election cycles.

San Antonio Mayor Julian Castro (D), a rising Democratic star who delivered the keynote address at the Democratic National Convention, told The Post that he thinks Texas will “go purple and then blue within the next six to eight years.”