But a new paper, recently published in Contemporary Economic Policy (pdf), sheds light on the reasons why—and why this disparity matters.

Analysts polled a representative group of more than 1,000 participants in 2009, asking a number of questions about water consumption as well as attributes of bottled water in terms of taste, safety and convenience. Researchers confirmed that Black and Hispanic respondents were much more likely to drink bottled water and believe it was safer.

“The preferences of these minority groups are not driven by concerns about convenience, but rather perceptions about water quality,” the study said.

The economists then included data from the US Environmental Protection Agency on water quality violations for states, and found that people who lived in states with more water quality violations were indeed more likely to drink bottled water. The authors then presented indirect evidence in the form of previous research from the American Housing Survey (tables) that said Blacks and Hispanics are overrepresented as a share of those living with unsafe drinking water. They wrote:

For owner-occupied units, the percentage of housing units with unsafe drinking water from their primary source is 6% for the population overall, 9% for Blacks, and 16% for Hispanics. For renter-occupied units, the corresponding percentages are even higher—11% overall, 11% for Blacks, and 21% for Hispanics.

These findings are consistent with previous studies. For instance, a 2011 study published in JAMA Pediatricsfound African-American and Latino parents were more likely to give their children mostly bottled water. And a separate paper published in 2007found that many Latino families don't drink tap water because of concerns that it could cause illness.

“We now have an understanding of why people do this,” said Joel Huber, a marketing professor at Duke University's Fuqua School of Business, a co-author on the paper.

Of course, these results are based on broad aggregates, which mean they may not hold true for any individual. Still, such findings matter.

For instance, if policy makers want to use taxes to discourage bottled water consumption for environmental reasons, it means the tax would fall hardest on Blacks and Latinos.

There might also be public health implications, not so much related to bottled water consumption, but to aversions to cheaper tap water. Some studies have linked mistrust of tap water to lower consumption of water, and increased consumption of sugary drinks.

Source: Published originally on Quartz.com as Blacks and Hispanics drink more bottled water. Economists now know why, by Matt Phillips, June 29, 2015.