Mardi Gras has been dubbed the “Greatest Free Show on Earth,” thanks in large part to the magnificent Mardi Gras parades that entertain the crowds on the streets of New Orleans. But make no mistake, Carnival season puts a lot of money in motion in the local economy, and a recent study from two Tulane University economists helps shed new light on its impact.

In the past, the city has extrapolated the size and success of a Mardi Gras celebration from the weight of trash left behind. But professors Paul Spindt and Toni Weiss started their research by collecting data from krewes and a wide range of local businesses to determine how much money locals and visitors spend in the name of Carnival time. The study, commissioned by a group of Carnival krewe captains, counted costs ranging from parade throws and catering contacts to jewelry commissioned as ball gifts and hotel rooms booked by visitors.

They concluded that the 2009 Mardi Gras celebration brought a direct economic impact of $145.7 million and an indirect impact of $322 million to the city of New Orleans, and that this all resulted in a handsome return on taxpayer costs associated with parades, such as police overtime and added sanitation work.

“For every dollar the city spends, it gets $4.48 back,” says Spindt. “That’s not a bad investment. Any time you’re getting that kind of return, you’re doing pretty good.”

This study differs from earlier economic analyses of Mardi Gras because Spindt and Weiss focused only on Orleans Parish, rather than a multi-parish metro area. They also used a conservative methodology, counting only the expenditures for which they could find firsthand data or create reliable proxies, and so they say their findings are the “lower bound” of Carnival spending.

Further, their research tackled the issue of spending outside of Carnival season that’s still tied to the Mardi Gras image and the city’s association with the holiday. For instance, they explain, when tourists buy beads in the summertime or when conventions book “mini Mardi Gras” parades as event entertainment, they contribute to the indirect, but year-round, economic impact of the celebration.

“To ignore that is to ignore the full impact of Mardi Gras,” says Weiss. “While we might look at it as a 12-day event, it really defines the city for a lot of visitors. They come to New Orleans because of the allure of Mardi Gras.”