Amazon.com Inc. shoppers in the U.S. spent less per order during the first 32 hours of the annual Prime Day sale than the previous two years, according to Numerator, suggesting shoppers are flocking to the site to buy diapers and cereal rather than flat-screen televisions and laptops.

Shoppers aren't showing any signs of getting tired of Amazon Prime Day, even though some sellers had said they weren't planning on offering deals this year.