As a startup founder, you may have considered whether or not you should give up equity to join an accelerator. Now a report released at South By Southwest ranking the 15 best accelerators in the U.S. has made that decision a little easier.

According to the 2013 Rankings of Top U.S. Seed Accelerators, Y Combinator is the best accelerator in the country, based on several metrics. TechStars and AngelPad rank second and third, respectively. The rankings were compiled by MIT Sloan School of Management professor Yael Hochberg and professor Susan Cohen of the University of Richmond and the Batten Institute at the University of Virginia's Darden School of Business.

"The goal of the seed accelerator rankings project is to start a larger conversation about the accelerator phenomenon, its effects, and its prospects for the future," Hochberg said during her presentation at South By Southwest, TechCrunch reports. The rankings are also an effort to inform entrepreneurs about which programs are worth the stake.

Based on their research and data from CrunchBase, Hochberg and Cohen ranked the accelerators based on the valuations their portfolio companies achieved in the years after graduation; the number of exits an accelerator has had; whether or not startups received additional financing rounds after the programs; the percentage of startups still up and running; how venture capitalists feel about the programs; and how the entrepreneurs in the programs feel about their experience.

The good news is that 90 percent of entrepreneurs surveyed said they would do it over again, and 95 percent said the accelerator they attended was worth the equity stake they gave up, TechCrunch reports.

Here are the 15 best startup accelerators in the U.S., according to the researchers.