One advantage of crowds over traditional teams is that crowds enable the assembling of a large number of individuals to address problems. The literature is unclear, however, about when crowd size leads to better outcomes. To better understand the effects of crowd size we conducted a study on the retention and performance of 4,317 articles in the WikiProject Film community. Results indicate that crowd composition, specifically diversity and experience, is vital to understanding when size leads to better retention and performance. Crowd size was positively related to retention and performance when crowds were high in diversity and experience. Retention was important to determining when crowd size led to better performance. Crowd size was positively related to performance when retention was low. Our results suggest that crowds benefit from their size when they are diverse, experienced, and have low retention rates.