More than 77 percent of wireless subscribers in the U.S. subscribe to or purchase text-message capability, says Nielsen Mobile. And uers now send and receive more text messages than they do voice calls.

In the United States, about 200 million of the 259 million wireless subscriber lines subscribe to or purchase text-message capability. Of these, 138 million--53 percent of all mobile subscribers--use text-messaging on a regular basis.

Nielsen recently reported that in the second quarter of 2008, mobile subscribers sent or received an average of 357 text-messages per month, compared with 204 phone calls. And while the average number of text-messages sent or received has increased 351 percent (from 79 text-messages sent or received last year), phone traffic have not become less popular.

In fact, phone useage has been constant, suggesting that text messaging adds to, rather than replaces, voice communications.