Nearly 180 million Americans shopped during the five-day holiday shopping period from Thanksgiving Day through Cyber Monday, according to the National Retail Federation's (NAR) annual survey released Tuesday.

In total, 179.8 million unique shoppers made in-store or online purchases during the 5-day weekend, which is seen as the official start of the holiday shopping season, according to the NRF. That figure was down from last year's total of 186.4 million, but in-line with the average of the last four years.

"Over the last few years consumers have shifted their holiday shopping plans to start earlier in the season," said NRF Chief Executive Matthew Shay in a press statement.

The NRF's survey highlights how consumers are shifting towards a longer holiday shopping season as big retailers like Amazon (AMZN  ), Target (TGT  ) and Walmart (WMT  ) launched Black Friday-style events and deals as early as October. According to the survey, 84% of shoppers already started their shopping ahead of Thanksgiving weekend, and 52% said they have completed more than half of their planned purchases.

That consumer shift is evident in data released Tuesday by Adobe Analytics--which analyzed more than 1 trillion visits to retailers' websites--that showed that consumers have already spent $109.8 billion online this holiday season, up 11.9% over last year, with e-commerce shoppers only spending $33.9 billion during the Thanksgiving weekend. The latter figure was down 1.4% year-over-year in total, as big shopping days like Black Friday and Cyber Monday marked their first ever declines since Adobe started reporting on e-commerce in 2012, falling 1.3% and 1.4%, respectively.

"With early deals in October, consumers were not waiting around for discounts on big shopping days like Cyber Monday and Black Friday," said Taylor Schreiner, director of Adobe Digital Insights, in a press statement. "This was further fueled by growing awareness of supply chain challenges and product availability."

Despite the slowdown, Adobe expects this holiday season to be record breaking in-terms of e-commerce activity. So far, the firm has recorded 22 days that have topped $3 billion in online spending, setting a new milestone. Last year, only 9 shopping days in the season topped $3 billion by the end of November. Adobe expects the entire season--Nov. 1 through Dec. 31--to hit $207 billion, which would represent record gains of 10%.

Forecasting for both online and in-store purchases, the NRF estimates that U.S. retailer sales will rise by a record 8.5% to 10.5% year-over-year from November through December, totaling as much as $859 million for the season.