Online retail sales in the U.S. will grow solidly in coming years, helped in part by consumers' broad Internet connectivity options and their increased familiarity and satisfaction with e-shopping, according to Forrester Research.U.S. online retail sales, which rose 12.6 percent to US$176.2 billion in 2010, are expected to grow at a compound annual rate of 10 percent through 2015, after dampening in 2008 and 2009 due to the economic downturn."Forrester remains bullish on the future of e-commerce," wrote analyst Sucharita Mulpuru in the report, "U.S. Online Retail Forecast, 2010 To 2015: eCommerce Growth Accelerates Following "The Great Recession."In 2010, almost a third of the growth came from the 5.5 million new online shoppers, mostly younger and older people, as well as adults of all ages who until last year hadn't felt comfortable enough with technology to make e-purchases.The bulk of the growth, however, came from existing shoppers, many of whom spent more online than in 2009, not only in categories that are online staples, like books and media, but also in products mostly sold in physical stores, like furniture and home appliances.Forrester Research expects online shopping to snatch an increasingly higher share of sales away from physical retail outlets, as consumers are drawn to e-stores by their convenience, prices and inventory variety.In 2010, 8 percent of U.S. retail sales were generated online, but that share is expected to increase to 11 percent by 2014. Respondents ranked the online sales channel first along with physical discount stores when Forrester asked them to pick the one they plan to spend more money on in the coming year.Factors helping U.S. e-commerce include an expanding ability to go online not only from work or home PCs, but also via mobile phones, tablet devices, video game consoles and Internet-connected television sets, Forrester said.Shoppers are also attracted to e-stores by their broader variety of products, as well as by new shopping models, like online daily deal offerings, flash sales, digital book and music downloads and the ability to customize merchandise.Convenience is also a major factor, especially during busy shopping days or seasons. For example, 83 percent of the Forrester survey respondents said they prefer shopping online to braving the crowds at brick-and-mortar stores during Thanksgiving weekend.