Same-sex couples in some parts of the United States have been able to wed for long enough to conclude that expanding gay marriage to other states would not undermine traditional marriages, a University of Massachusetts economist testified during a trial on California's same-sex marriage ban.

Lee Badgett's testimony Tuesday finished off the sixth day in the historic trial. Badgett took the witness stand on behalf of two same-sex couples suing to overturn Proposition 8, the state's voter-approved ban. She cited statistics from Massachusetts, which has allowed gay couples to marry since 2004, showing that marriage and divorce rates for straight couples have not been affected.