Experts speaking before a trial on California's gay marriage ban have said that lifting it would make people healthier and generate more money for the state's economy.
The federal trial is examining whether Proposition 8, which banned gay marriage in California, is constitutional.
Yesterday, San Francisco's chief economist Edmund Egan said that the city could see its economy boosted by millions if gay couples were allowed to marry.
According to AFP, he argued that if more gay people married, they would increase school district revenues, real estate, payroll and sales taxes and would be more likely to be insured.
Egan added that married people spend more than their unmarried counterparts and tend to be wealthier.
He said: "The long-term cost of discrimination weakens people's productivity in the workforce. Higher productivity leads to higher wages and higher wages lead to higher payroll taxes for the city."
Egan estimated that gay marriage could boost economic revenues in other ways in California, such as money spent by couples on their weddings and hotel rooms.
During cross examination, a lawyer for Protect Marriage countered that not all gay couples would get married, and that Egan had not considered the spending which would be necessary to allow gay marriage.
Meanwhile, Ilan Meyer, a social scientist from Columbia University, argued that the stigma of not being able to get married can result in increased risks of depression, suicide and drug abuse.
On civil unions, which the pro-gay marriage lawyers argue is inadequate, Meyer said: "Having a second type of an institution that is clearly not the one that is designed for most people clearly is stigmatising."
Today, Michael Lamb, a Cambridge University psychologist, is expected to discuss the benefits of marriage for gay couples who have children.
The case has been brought by two gay couples, Kris Perry and Sandy Stier, of northern California, and Paul Katami and Jeff Zarrillo, who live in southern California.
Gay marriage was legalised in California in May 2008. Voters banned it under Proposition 8 the following November. The estimated 18,000 gay couples who were able to marry in that brief window have been allowed to remain married.
This week, the Supreme Court placed a ban on allowing proceedings to be shown on YouTube.
The gay couples and their lawyers supporting the broadcasting, but gay marriage opponents said they would be harassed and placed in danger, despite conducting a highly publicised television campaign against gay equality.
According to the San Francisco Chronicle, the court received more than 138,000 comments from members of the public about the decision, with all but 32 calling for the trial to be broadcast.