More than 9,500 participants’ accounts were examined, none of whom earned more than $200,000 in any given year. The workers spanned 29 U.S. locations. Three-quarters were hourly workers, and 83 percent were male. In terms of race, 83 percent were white, 8.3 percent African American, and 5.8 percent Hispanic.

At the end of the study period, the median 401(k) account balance was just over $52,500.

However, the median account balance for whites between 40 and 60 was near $90,000.

For Hispanics, the median balance was near $50,000, while for African Americans it was near $30,000.

Even younger whites, those ages 20 to 40, had median account balances that were higher than the middle-age African Americans.

The disparity is explained, in part, by much higher rates of non-participation among both African Americans and Hispanics, the researchers said.

When they do participate, Hispanics tend to defer equal amounts of income as whites. But the study showed African Americans contributed about 2 percent less of their income to the plan than whites.

Minorities were also only half as likely to invest in stocks as whites were, and twice as likely to invest in conservative money-market funds, clearly affecting returns on accounts, and ultimately balances.

And both Hispanics and African Americans drew down their 401(k) balances through withdrawals and loans at a higher rate than whites, with African Americans also withdrawing much more than Hispanics.

The paper attempts to speculate how financial literacy affects savings habits by separating data of salaried and hourly workers, a “crude” way of estimating financial literacy, admitted the researchers.

Nonetheless, salaried African Americans were still less likely to participate than salaried whites, whereas salaried Hispanics participated at rates similar to whites.