Forty-seven percent of all U.S. smartphone owners used mobile shopping applications in June 2012, according to new Nielsen research.

Roughly 45 million American smartphone owners now access apps in the Shopping/Commerce category, using these mobile services an average of 17 times per month, Nielsen reports. eBay leads all mobile apps with more than 13.1 million unique monthly iOS and Android users averaging about 64 minutes of shopping activity per month; Amazon is next at 12.1 million unique monthly mobile users and 18 minutes per month, followed by daily deal platform Groupon at 11.9 million and 21 minutes.

During June 2012, 13.2 million smartphone owners used the eBay Mobile application, from Android/iPhone handsets in the U.S.

In addition to mobile apps that extend established brick-and-mortar and/or online shopping experiences to mobile devices, Nielsen's Top Ten rankings include a number of apps designed to engage consumers in retail locations. Shopkick, which offers rewards points called "kicks" to smartphone users who enter stores, scan consumer goods and make purchases, ranks fourth overall with 6.4 million users averaging close to 3 hours, 20 minutes per month; barcode scanning tool RedLaser ranks eighth overall with 1.9 million users averaging 4 minutes per month, followed by shopping list app Out of Milk at 1.7 million users at 31 minutes a month.

"Retailers are finding that consumers are willing to use smartphone apps to enhance their shopping experience, and this data shows usage of shopping apps is growing," said Nielsen's Director of Telecom Insights Don Kellogg. "As more Americans use their smartphones while shopping and making purchases directly through apps, retailers should consider personalizing their targeted offerings around the needs of individual consumers."