BOSTON ( TheStreet) -- As same-sex couples are increasingly being granted rights similar to those of traditional marriages, many will be at a comparative disadvantage as they enter retirement. The study by the Williams Institute at the UCLA School of Law says gays and lesbians will have less retirement income and fewer ways to pass savings on to their families after their death. Merrill Lynch, a unit of Bank of America ( BAC), helped fund the report. A large share of same-sex couples will be entering retirement in the next two decades, just as states open marriage and civil-union laws. There are about 1.2 million gay people living with a same-sex partner in America, according to the most recent U.S. Census. Inequality in retirement savings needs to be addressed, says Naomi Goldberg, author of the survey, titled "The Impact of Inequality for Same Sex Partners in Employer-Sponsored Retirement Plans." The study, citing census statistics, shows that traditional couples earn an average of 4% more in combined household retirement income each year compared to same-sex couples. It claims, however, that the statistic only tells part of the story. Same-sex surviving spouses can't directly receive the balance of their deceased spouse's 401(k) plans. Because they must begin making withdrawals immediately, they face a higher tax rate and the loss of accruing interest. Surviving same-sex spouses also pay higher estate taxes. "The bulk of these inequalities are a direct result of the Defense of Marriage Act (DOMA), which forces the federal government to treat same-sex couples differently than married couples when it comes to retirement savings or estate taxes after death," Goldberg says. DOMA was passed under President Bill Clinton. There have been changes that have benefited gays and lesbians. The Pension Protection Act of 2006 gives surviving partners of same-sex relationships access to retirement assets.