By Kevin Kelleher
November 19, 2012

FORTUNE – Some day in the future, anthropologists may be able to explain the bizarre shopping rituals of the 21st Century American consumer during the holiday season: Why, for example, so many people look for bargains on one day – Black Friday – when with a little work bargains can be found on the other 364. Or why they stand in midnight lines in bleak winter weather only to risk stampedes and fight each other for cheap gifts.

Herd behavior is also common among online holiday shoppers, with people doing a lot of their shopping on days that have been come to be called Cyber Monday. And of course, there are always the buying surges inspired by last-minute shoppers. In fact, the rituals of holiday shoppers are so predictable that marketers have learned to craft retail campaigns around certain days.

This year, the holiday season is expected to see strong growth, as a slowly but steadily rising consumer confidence prevails over concerns about a global recession in 2013. The National Retail Federation estimates that total holiday sales this season will rise 4.1%, above the 3.5% average for the previous 10 years. The NRF has a tendency to be conservative in its estimates. Last year, it initially projected a 2.8% rise in holiday sales, but the actual figure was 5.6%.

MORE: Jeff Bezos: The ultimate disrupter

A survey by consulting firm Accenture found that 52% of U.S. consumers will increase their spending this year by $250 or more, with consumers on the whole spending an average of $582. And 53% say they plan to brave the crowds on Black Friday, up from 44% this year (although the survey was taken before a Black Friday strike at Walmart (WMT) was a possibility.)

As usual, online shopping will see bigger gains. sees e-commerce sales for all of November and December growing 12%. And numbers released Monday from Adobe (ADBE) see holiday sales growth more modest: between 7% and 10%. (Adobe’s estimates are based on the 33 days between Thanksgiving and Christmas, a period that was only 29 days long last year.)

One reason for the discrepancy in online-sales forecasts is how the numbers are calculated., an online-retail trade group, relies on data from the Commerce Department, the Conference Board and the NRF. Adobe looks at e-commerce data from 500 retailers using its content and marketing data to power their sites, using algorithms to account for new trends like social marketing and mobile shopping,

Drawing on 150 billion visits to retail sites, Adobe noticed several peaks during the holiday season. The biggest one, of course, is Cyber Monday. Back in 2005, the theory behind Cyber Monday is that consumers used Thanksgiving weekend to research and think about which gifts they’d buy online. Come Monday, they’d return to high-bandwidth connections of their offices and make purchases.

MORE: The best of everything in tech this year

Since then, home Internet connections have gotten faster and Cyber Monday is a day when retailers tailor bargains for online shoppers. Adobe expects Cyber Monday sales to rise 18% this year to $2 billion. The second busiest online-shopping day is expected to be Black Friday, which will see a 12% bump in sales. That’s thanks in good part to mobile devices, which will account for 24% of visits to e-commerce sites.

Sales from mobile devices will play a bigger role than ever this holiday season, rising 110% to account for 21% of all online sales, Adobe predicts. Two-thirds of those mobile sales will come through tablets, and the other third through smartphones.

In fact, mobile devices and social networks are helping traditional retail brands forge closer ties with customers. Some of them are using text messages and push notifications to offer discounts to loyal customers, while others are enlisting them to be brand ambassadors for social sites like Pinterest. “Mobile is helping retailers have better relationships with people,” says Brad Rencher, vice president of digital marketing at Adobe.

The 2012 holiday season is shaping up to be a moderately busy one, most likely the strongest since the financial market turmoil of four years ago. That may make the Black Friday frenzy even crazier than it’s been in a while. But for those who prefer the more sedate alternative of online shopping, there will be plenty of bargains as well.

You May Like