Washington state's economy could get an $88 million boost from legalizing gay marriage.

Governor Chris Gregoire's plan to make Washington the seventh state to legalize gay marriage took a dramatic leap forward on Wednesday when the Washington Senate approved a marriage equality bill by a wider margin than expected. Supporters say they have more than enough votes in the House to approve the legislation.

According to a report issued by the California-based Williams Institute, the weddings of gay and lesbian couples are estimated to add $88 million to the state and local economy of Washington over the course of three years and provide a $57 million boost in the first year. The study's most conservative estimate is $18 million over the law's first three years.

The report estimates that half of the 19,003 resident same-sex couples, or about 9,500 couples, will choose to marry during the law's first three years.

Louise Chernin, president of the Greater Seattle Business Association, told Q13fox.com that marriage equality will also boost tourism.

“We are working with the convention and visitors bureau,” she said. “We've been working for the last year and a half, encouraging people to visit our beautiful state; this will be one more attraction.”

The report's spending estimates do not include revenue generated by out-of-state couples who decide to marry in Washington. According to Census figures, there are more than 129,000 gay couples living in the five states that send the most visitors to Washington.