In this Monday, Dec. 12, 2016, file photo, an online shopper searches a site. On Tuesday, Nov. 28, 2017, the National Retail Federation estimated that people who shopped both online and in stores from Thanksgiving to Cyber Monday, spent more than those who stuck to one or the other. (AP Photo/Wilfredo Lee, File)

A retail trade group estimates that people who shopped both online and in stores from Thanksgiving to Cyber Monday spent more than those who stuck to one or the other.

The National Retail Federation estimated Tuesday that more than 174 million Americans shopped in stores and online during those five days, higher than its previous 164 million forecast. The group finds those who shopped online and in stores spent or were planning to spend $82 more on average than online-only shoppers, and $49 more on average than -only shoppers.

Meanwhile, Adobe Analytics says Cyber Monday was the biggest U.S. online shopping day ever, with a record $6.59 billion spent, up 17 percent from last year.

The NRF said the average expected spending per person was $335.47. The group didn't offer a comparable number from last year because it changed its methodology, but said it was in line with expectations. About 75 percent of the spending went specifically toward gifts, and the biggest spenders were people aged 25 to 34, who spent $419.52 on average. The group surveyed more than 3,200 people Saturday and Sunday about their spending so far and their plans.

"We are encouraged that we are starting from a position of strength," said Matthew Shay, CEO and president of the NRF. But he warned that the weekend is not a definite predictor of the rest of the holiday period. The Thanksgiving weekend traditionally kicks off the holiday shopping season, but stores have increasingly started their sales earlier in the month.

More than 64 million planned to or shopped both online or in stores from Thanksgiving to Cyber Monday, the NRF said, while more than 58 million were doing their shopping online only and over 51 million were going to stores only.

The higher spending from those who go back and forth to stores and online underscores how retailers need to offer services that make it easy for shoppers to switch back and forth. It also highlights the importance of physical stores to expand their online business, while more online retailers find they need to have a physical presence. Online leader Amazon has entered into the holiday season with a newly magnified brick-and-mortar presence, with more than a dozen Amazon Books stores, which also sell toys, electronics and small gifts.

Cyber Monday was the biggest U.S. online shopping day ever, according to Adobe Analytics, the research arm of software maker Adobe. The company said $6.59 billion was spent online on the Monday after Thanksgiving, up nearly 17 percent from the year before. And $2 billion came from shoppers who were buying from their smartphones, also a record, Adobe said.

The numbers show Cyber Monday is still a draw, even as retailers are spreading out their deals over more days.

"It's become a habit and tradition for some people to look what's out there on Monday," said Sucharita Mulpuru, a retail analyst at Forrester Research.

Shay reiterated the group's forecast that will be up as much as 4 percent, but he doesn't anticipate it will be higher than that. Last year, holiday sales, which exclude sales from autos, gas and restaurants but includes online spending, rose 3.6 percent.

And despite an improving economy, shoppers are still fixated on deals. Last year, the NRF found that more than a third of customers surveyed said that all of their purchases were on sale. The group said the level was similar this year.