Business accelerators like Y Combinator and TechStars have come to occupy a critical geography in the tech landscape, and today two professors are announcing the results of their survey to determine which ones have come out on top at South By Southwest.

“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,” according to a presentation by Professor Yael Hochberg, a faculty member at the MIT Sloan School of Management.

Hochberg and her colleague, Professor Susan Cohen of the University of Richmond and the Batten Institute at the University of Virginia’s Darden School of Business, used original research and data from CrunchBase to determine the best 15 accelerators in the U.S. Those accelerators were then grouped into Gold, Silver and Bronze categories to reflect how they performed in a series of categories. Here are the best:

1. Y Combinator (Gold)

2. TechStars (Gold)

3. AngelPad (Gold)

4. Launchpad LA (Silver)

5. MuckerLab (Silver)

6. AlphaLab (Silver)

7. Capital Innovators (Silver)

8. Tech Wildcatters (Silver)

9. Surge Accelerator (Silver)

10. The Brandery (Silver)

11. Betaspring (Bronze)

12. BoomStartup (Bronze)

13. Entrepreneurs Roundtable Accelerator (Bronze)

14. JumpStart Foundry (Bronze)

15. DreamIt Ventures (Bronze)

Business accelerators like Y Combinator and TechStars have managed to capture the imagination of entrepreneurs and seed investors. They have spawned a host of copycats backed by corporations and cities around the world looking to capture some of the entrepreneurial energy unleashed by early-stage companies.

The proliferation of these ventures has caused some in the industry to worry about the potential for an accelerator bubble.

Most accelerators provide a stipend or small seed investment, mentoring, and workspace and professional services in exchange for an equity stake in the company. Typically the equity investment is around $25,000 and the equity stake is roughly 6 percent, according to Hochberg’s research.

To be included in the rankings, accelerators needed to have graduated at least one cohort by 2013, be based in the U.S. and have at least 10 graduates in their class.

Hochberg measured the accelerators based on the valuations their portfolio companies achieved in the years after graduation; the number of exits an accelerator has had; the ability of companies to receive additional financing after they left an accelerator program; the percentage of an accelerator’s portfolio that was still in operation; the opinion venture investors have of the accelerator program; and finally the opinion that graduating entrepreneurs had of their experience.

Two years out from graduation, the valuation of all portfolio companies was bout $5 million and the average valuation of a priced round or exit was $11 million. Both of those numbers are significantly lower than the average valuation across all portfolio companies in accelerators — $17 million. And the average valuation of all portfolio companies on a priced round or exit was $29 million.

Another key metric is follow-on financing. Roughly 59.3 percent of all companies in accelerator programs have gone on to raise follow-on financing. Across portfolios, the average raise was $1.8 million through either internal or external rounds and $2.8 million for companies that just raised outside funding.

As for exits, it’s far too soon to tell. Historically a venture investment takes around seven to nine years to exit, and the oldest accelerator program — Y Combinator — is only nine years old itself. The average accelerator program is only 3.1 years old and has only graduated nearly seven groups of companies. Across all startups invested by accelerators, only 2.1 percent have had a meaningful exit, according to the report.

No matter what the results are, entrepreneurs are almost universally happy with the accelerator experience. Roughly 90 percent of the ones Hochberg and Cohen surveyed said they would repeat the experience, and 95 percent said it was worth it to give up the equity.

Photo via Flickr user Global Jet