Earlier this year, the Williams Institute issued a report showing that allowing same-sex marriage in Illinois would generate $54-103 million in new spending in the state over the first three years.
"We estimate that as many as 11,525 same-sex couples who live in Illinois would choose to marry in the three years following an opening of marriage to same-sex couples in that state," wrote Angeliki Kastanis and M.V. Lee Badgett.
The report also noted:
The total spending on wedding arrangements and tourism by 11,525 same-sex couples and their guests would add an estimated $103 million boost to the state and local economy of Illinois over the course of three years, with a $66 million boost in the first year alone.
This economic boost would be likely to add $8.5 million in tax revenue to state and local coffers, with an estimated $5.4 million occurring in the first year.
Conservatively, if many same-sex couples have already married, or if all of the estimated 5,400 existing Illinois resident same-sex couples who are in civil unions were to marry or convert their civil union into a marriage without holding a celebration, the estimated rise in wedding spending and tourism would be lower, or approximately $54 million over the first three years. This modified increase in spending would translate to $4.5 million in tax revenue.
This report does not include spending estimates for out-of-state same-sex couples, many of whom might travel to Illinois in order to marry, spending additional funds on wedding planning and tourism during their brief stay.
See williamsinstitute.law.ucla.edu/wp-content/uploads/IL-Econ-Impact-Mar-2013.pdf .