In a holiday shopping season synonymous with crowds, deep discounts and deal-crazed shoppers trampling each other, Cyber Monday stands out as a day when consumers are encouraged to stay home -- while still opening up their wallets, of course. And with Thanksgiving weekend sales lower this year than in 2012, and experts forecasting modest holiday season sales growth, Cyber Monday may be retailers' best hope for meeting sales goals.

A National Retail Federation weekend survey found that 131 million people are planning to shop online today, up from 129 million last year. Shop.org, a division of the National Retail Federation, predicts that online sales will grow between 13 and 15 percent this holiday season, totaling as much as $82 billion in the months of November and December.

More of this activity will happen on mobile devices than ever before. Nearly one in five Cyber Monday consumers, or about 25 million people, said they plan to use their mobile device this year, a 22 percent increase from last year's 20 million mobile shoppers.

Shop.org, invented Cyber Monday in 2005 as an extension of the Thanksgiving weekend shopping holiday, promoting it as a day for online sales. By 2010, it had become the biggest day of the year for e-commerce, and this year more than eight in 10 retailers plan to offer Cyber Monday promotions.

They could use the extra business. Total sales on Thanksgiving weekend fell 3 percent this year to $57.4 billion, according to the National Retail Federation. Although 141 million people shopped from Thursday through Sunday, up from 139 million last year, their spending averaged only $407.02, down from $423.55 during the same weekend of 2012.

Even as overall sales numbers decline, however, online shopping continues to grow. Rather than waiting for Cyber Monday, 42 percent of Thanksgiving weekend shoppers, or about 59 million people, made purchases online, the trade association said.

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