Playnomics recently published their third quarter 2012 social player engagement report. In this report, they found that almost 95 percent of all U.S. players acquired in the first part of Q3 were inactive by the end of Q3 and about 85 percent of U.S. players acquired in Q3 do not return after their first day.
U.S. females churn at slightly higher rates than U.S. males but tend to play longer before doing so. Also non-churners play about twice as long on their first day as eventual churners.
Other interesting trivia shows that while players are most likely to play on Saturdays, they play the longest on Mondays. Friday and Saturday is also when players are likely to pay the most in these social games.
The study found that play time tended to be cumulative the longer a player is engaged. Even getting a player to return after one day yields significant dividends.