Even though voice-only services account for 95 percent of wireless carriers’ revenues, the research firm says that within the next year voice-only subscribers will reach 120.7 million, up from 114.3 million in 2001, and voice and data users will nearly double to 22.3 million, from 11.4 million.

By 2006, voice-only subscribers will fall to 100.4 million while voice plus data users will rise to 96.3 million.

These figures are encouraging, but Knox Bricken, Wireless/Mobile Services analyst with the Yankee Group, cautions wireless carriers that success in the wireless data market is "burdened with new challenges."

Bricken says, "There are numerous facets that need to align in order to ensure success in wireless data: networks must be upgraded, handsets must be distributed, appealing content needs to be available, and the customers must be taught how to effectively use the data services."

With churn rates well over 25 percent, and continuing to escalate, the study says that wireless data may serve as an effective tool to increase customer retention, thus increasing the profit per customer.

Bricken told Newsbytes that the availability of new data-enabled handsets and the rolling out of 2.5G services are positive incentives to get people to sign-up for wireless data services.