On the Monday before Christmas, 49.2% of all online sales in the United States were made on Amazon, according to data from Slice Intelligence.

Consumers were doing their shopping later, secure in the knowledge that Amazon’s two-day delivery would still get them what they’d ordered before it was too late.

“Digital has taught people they can wait to the last minute,” said Brendan Witcher, principal retail analyst with Forrester. By the final week before Christmas “consumers don’t have the time or luxury to be shopping around anymore,” he said.

This shift has been coming for several years but is accelerating, said Ken Cassar, principal analyst at Slice.

“Even five years ago, if you ordered something on Monday, Dec. 19 you would have been very worried as to whether your present was going to make it on time,” he said.

This Christmas, Amazon customers seem to have become comfortable with a new normal. The Seattle company’s largest share of online retail hit on Dec. 18, 19 and 20, at 47.8%, 49.2% and 48.2% respectively.

There’s was another big bump on Christmas day itself, when Amazon’s total share of online sales shot to 46.1%. That seems to be wildly last minute purchases relying on Amazon Prime Now’s two-hour delivery promise.

“We are really seeing the shape of the holiday sales curve morph. … This shows very clear validation of the investment that Amazon has made over the past couple of years in putting inventory and fulfillment centers closer to consumers,” Cassar said.

The Slice data is based on its analysis of over 1 million digital shopping receipts. It counts Amazon’s own sales and those of third parties that sell on the site. It doesn’t count Amazon-owned properties such as Zappos and Fabric.com.

Amazon’s holiday seasonal sales began relatively slowly, the Slice data shows. On Black Friday its share of online sales was 25%. That increased in almost a straight line to Dec. 19, that last Monday before Christmas.

It wasn’t until Dec. 23 that the Seattle company’s market share began to consistently drop below 38%

“It used to be with online that by Dec. 14  or 15 you would see sales hit a high and then fall off. But Amazon was still going gangbusters until the 19th,” Cassar said.

Which isn’t to say that everyone waits until the last minute to do their holiday shopping. Over 40% of sales still happen in November, said Witcher. And more than half of consumers told a National Retail Federation survey that they expected to buy their last Christmas gifts earlier than Sunday, Dec. 18.

But that still left a lot of people busy shopping the week before Christmas, which fell on a Sunday.

The high Monday sales aren’t surprising, said NRF spokeswoman Ana Serafin Smith. Increasingly retailers are seeing a trend that’s been dubbed “Green Monday,” which is a big boost in purchases on the last Monday before Christmas.

“In this particular year, because of when Christmas fell, that day was a big one for all online retailers,” she said.

The numbers represent the Seattle company’s dominance in the online retail space. A study released in September found that 55% of shoppers begin their shopping searches on Amazon, no matter where they end up buying.

Overall, Amazon’s share of the 2016 holiday online market share was 38%. That’s not much larger than it was the year before, when it was 37.9%, Slice found.

The lack of overall movement isn’t a surprise to Cassar because Amazon’s overall sales are so high that it would take close to $200 million in sales to grow its share by a single percentage point.

“For Amazon to move the needle, you have to recognize that it’s a really big needle to move,” he said.

By Elizabeth Weise for usatoday.com |Photo: Pixabay