A new look at an old problem in demography: when people no longer identify with their ethnic group. 

Given all of the anti-immigrant -- and specifically anti-Mexican -- rhetoric coming from Republican presidential primary candidate Donald Trump, it may seem odd when he wins the Latino vote in a heavily Hispanic state, such as he did this week in Nevada. Part of the confusion comes from unclear demographic definitions, especially when it comes to the term "Latinos" in contemporary America.

When is a Latino no longer a Latino? That was the focus of new research coming from the University of Colorado and University of Texas, which Quartz recently spotlighted.

Fluid Self-Identities

The Latino population in the U.S., the research found, is quite fluid, especially from generation to generation. Survey data about Latinos -- as categorized by birthplace or the countries of origin of parents and grandparents -- produces different results than surveys that categorize by self-identification.

For one big example, when self-identification is taken out of the picture, the Latino demographic turns out to be in a much better economic situation as a whole. Latinos under this definition are actually more educated on average than suggested by standard demographic profiles like the U.S. Census Bureau.

This could be because second and third-generation Latinos by ancestry choose not to self-identify as "Latinos." The trend is known in demography as "ethnic attrition."

"To some extent we're understating the progress of later-generation Hispanics," said Stephen Trejo, co-author of the latest working paper and economics professor at the University of Texas, Austin, to Quartz.

"And we're probably overstating the progress of Asians," he added, commenting on the differences in demography statistics that can arise from varying cultural standards of self-identification. "But the question is how much."

Nearly all first-generation immigrants identify with their country of birth, a full 99 percent according to the research. But second-generation and especially third-generation Latinos are often left out of that demographic when asked to self-identify their ethnicity.

Measures of Ethnic Identity Matter

The factors that underpin this ethnic attrition vary from the psychologically loaded to the mundane. Interracial or interethnic marriage, for example, is one factor. Another is "how Latino one feels" as an assimilated or bi-cultural Hispanic.

There are interesting correlations to be drawn from the data based on later generations that didn't identify as Latinos. Second-generation Latinos who didn't self-identify averaged nine months more education than those who did identify as Hispanic, and that trend only becomes more exaggerated in later generations. Economic success, social status and other quality of life factors are tied to education, so when later-generation Latinos are excluded from the demographics by not self-identifying, the data in those other areas gets skewed as well.

The relative demographic chaos created by the subjective nature of self-identifying ethnicities is enough of an issue that the U.S. Census Bureau has decided to make changes to the survey to more accurately pin down ethnic backgrounds. But for now, as the political primaries inspire obsession over the direction of the powerful Latino vote, various measures of just who is Latino and who is not will likely continue to be imprecise.

So as the Democratic and Republican primaries continue into more diverse and Latino-heavy states such as Texas, it's best to take the pollsters with a grain of salt when looking at who's winning the Latino vote. There can be a lot of variation depending on what questions are asked.