“According to the Pew Internet project, people in the 18-24 year-old range are sending and receiving 110 texts per day on average. The median number of texts sent/received by that group is 50 per day.
The overall average for texting per day amongst cell phone users is 42, says Pew. That number is flat compared on a year over year basis. Pew interviewed 2,277 people 18 and over for its survey.”
This Pew chart matches my observations: