The latest survey from the Pew Research Center's Internet & American Life Project - a report called Cell Phones and American Adults - shows that texting by American adults has increased substantially over the past year. 72% of adult mobile phone users now send and receive SMS text messages, up from 65% in September 2009. That compares with 87% of teenage mobile phone users (aged 12-17). Adults use their phones for around 5 voice calls per day and send an average of 10 text messages per day, whilst teens send 50 messages a day on average.
Overall, 5% of adult texters in the USA send more than 200 text messages a day. That figure's much higher for younger mobile users; 15% of teens 12-17 and 18% of adults 18-24 send more than 200 messages a day.
The report also notes that heavy users of mobile phones for messaging are also heavy users of the phone for calling, whilst light texters are generally light callers.