Airbnb guests helped contribute $56 million to San Francisco’s economy from June 2011 to May 2012 and outspent hotel guests, according to consulting firm HR&A Advisors. Only $12.7 million of that was spent on Airbnb lodging, while an additional $43.1 million is attributed to cash spent while the lodgers were in the city. Airbnb guests tend to stay longer in San Francisco than hotel-based tourists, clocking in an average of 5.5 days per stay compared to 3.5 for hotel guests. [Source: TechCrunch]