Report: Adults ages 18 to 24 exchange an average of 109.5 text messages a day.
Young adults are the most avid texters by a wide margin. Cell owners between the ages of 18 and 24 exchange an average of 109.5 messages on a normal day—that works out to more than 3,200 texts per month—and the typical or median cell owner in this age group sends or receives 50 messages per day (or 1500 messages per month).
Full version: http://www.pewinternet.org/2011/09/19/americans-and-text-messaging/