New York ? Employers have begun to discover troubling racial differences within their 401(k) retirement plans, a gap they say could leave today’s black workers far less financially prepared for retirement than whites.

Investor surveys and research by two large employers strongly suggest that blacks participate in retirement plans at far lower rates and are much less likely than whites to invest in the stock market. An industrywide study of 401(k) plan activity by race has never been conducted.

Exelon Corp., the country’s largest operator of nuclear power plants, discovered this year that about 15 out of every 100 black employees did not participate in its 401(k) plan, compared with around 10 of every 100 whites. It also found that one in three black employees contributed less than 5 percent of their pay to the plan, compared to just 14 percent of whites.

“We have to start addressing that now,” said Andrea Zopp, Exelon’s senior vice president of human resources. “If African Americans are not investing at the same rate, they will be behind,” she said.

McDonald’s Corp. discovered in 2004 that only half of its black store managers contributed to the company’s 401(k) plan, a lower percentage than whites. The company plans to announce at an event in New York that by auto-enrolling store managers into the plan it has reversed the trend; today, 95 percent of black restaurant managers are plan participants.

Few employers today peer into their plans in search of racial or ethnic differences, as they are required to do for discrepancies between high- and low-income workers. Fidelity Investments and Vanguard Group, two of the country’s largest retirement plan operators, both publish encyclopedic volumes on America’s investing habits that lack any reference to race or ethnicity.

Experts attribute lower investment rates to poor instruction on financial topics in public schools, and misconceptions about the risk of stocks within parts of the black community. Employers have also been urged to tailor their messages on retirement savings to account for what some black and Latino executives say are important cultural differences. And the federal government has been urged to strengthen its national strategy for financial literacy, which has been criticized as ineffective.

A survey by Charles Schwab Corp. and Ariel Mutual Funds concludes that four in 10 African Americans with household incomes of $50,000 or more have no money in stocks, compared to just one quarter of whites.

Ariel’s survey also found blacks who enrolled in retirement plans save a median $173 a month while whites save $252. The survey was administered in June and July and has a margin of error of about 4.5 percent.

A separate survey of retirees found whites are nearly twice as likely to have $100,000 or more saved than blacks, even when education, peak income level and other factors are held constant.