Amazon's Prime Day is fueling other retailers' online sales, an early reading shows.
On Monday, the first day of Amazon's 48-hour shopping extravaganza this year, retailers that make more than $1 billion in annual revenues saw a 64% increase in their digital sales compared with an average Monday, according to Adobe Analytics. That's better than a 54% spike last year, said Adobe, which measures transactions at 80 of the top 100 internet retailers in the U.S.
Niche retailers, which Adobe classifies as those that bring in less than $5 million in annual sales, saw a 30% increase in online sales on Monday, according to the firm.
Adobe said Amazon's Prime Day is now the third period outside of the holiday season during which online sales in the U.S. will top $2 billion, like they did on Labor Day last year and Memorial Day this year.
Amazon's Prime Day kicked off at 3 a.m. ET on Monday and runs for 48 hours, the longest in the event's history. Last year, Prime Day lasted 36 hours.
Other retailers including Walmart, Target, eBay, Macy's and Best Buy have been touting deals this week to compete. Target is pushing discounts for its in-house home goods brands. Walmart is expected to run deals, on everything from Google Home smart speakers to Instant Pots, through Wednesday this week.
More than 250 retailers altogether are expected to have sales going on to try to take advantage of the surge of web traffic around Prime Day, according to RetailMeNot, which tracks coupons online.
To be sure, it's unclear if shoppers are actually buying more around Prime Day through impulse purchases, or if they're just buying things now that they would've normally purchased later in the year. If the latter is the case, the week could end up only stealing sales from the back-to-school and holiday shopping seasons.
A study from Deloitte already shows back-to-school spending is expected to be about flat with last year, as more consumers are feeling price sensitive.
Amazon also said that its sellers worldwide on Monday had the biggest 24-hour sales day in the company's history, with millions of Alexa-enabled devices already sold.
Amazon shares are up more than 34% this year, bringing its market cap to more than $995 billion.