The nation’s wealthiest African Americans take a far more conservative approach toward investing than whites of similar means, according to a new report. The study, done by Credit Suisse in conjunction with the Institute on Assets and Social Policy at Brandeis University, found that the wealthiest 5 percent of African Americans—those with a net worth of $357,000 or better—pour a greater share of their holdings into relatively low-risk, low-reward investment vehicles, such as certificates of deposit, saving bonds, and insurance policies, rather than stocks, bonds and mutual funds.