It takes the average person 14 seconds to solve a CAPTCHA, with a 10% error rate

"According to a study recently conducted by UC San Diego researchers, spammers employ many hundreds of people, mostly overseas, to solve CAPTCHAs at the rate of about one dollar per thousand solutions. It takes the average person 14 seconds to solve a CAPTCHA, and the human error rate is ten percent. There are 3600 seconds in an hour, which means roughly 231 solutions per hour per person [(3600/14)(.9)], which means that the foot soldiers of the CAPTCHA-solving army get paid less than 25 cents an hour."
Source:  Data from UC San Diego researchers, reported by GeekOSystem, 13th August 2010
PDF of the full study here