A drop in mobile phone sales may be a signal that the weakening economy is taking a toll on consumers. In the second quarter, U.S. mobile handsets unit sales declined 13 percent to 28 million, compared to the same period one year earlier, according to NPD Group.

This marked the lowest figures since tracking the category began in 2005. “That lends credibility to the argument that the economy appears to be more of a factor than anything transpiring in the industry,” said Ross Rubin, director of industry analysis for NPD, Media Post reported.

Handset unit sales valued US$2.4 billion, dropping 2 percent from a year ago.

Average handset prices have risen 14 percent over the last year to $84, but were down by $3 since the first quarter, Media Post reported.

In spite of weakening sales overall, smartphones, such as the BlackBerry and the iPhone kept on growing from a 9 percent share one year ago to 19 percent currently.

“That may indicate there's a group of consumers that see value in wireless data and media and are willing to upgrade their phones to take better advantage of those capabilities. But there's still a large segment of consumers that can't justify the value in it,” Rubin added.

Besides carrying a higher retail price, smartphones also typically charge the additional cost of a data plan. According to Rubin, phones with QWERTY keyboards, which do not necessarily qualify as true smartphones, gained the most shares, from 12 percent to 28 percent of handset sales, Media Post reported.

In addition, 65 percent of phones purchased were capable of playing music, up from 45 percent a year ago. Also, 81 percent of them were Bluetooth-enabled, up from 69 percent.

Among handset manufacturers, though struggling, Motorola still led in U.S. market share during the second quarter, but by a small margin. Its share dropped from 32 percent to 21 percent, while Samsung and LG each claimed 20 percent, and Nokia and RIM made up 9 percent and 7 percent, respectively, according to Media Post.