Amazon.com's Prime Day sales were lower on the first day said Momentum Commerce. The company which manages online sales for 50 brands said its Amazon sales plunged 41% on Tuesday when compared with the start of Prime Day last year.

Amazon’s Prime Day event has grown to four days, but some signs point to a lack of consumer enthusiasm this year.

Including a delightful upholstery cleaner, an on-sale Dyson, $200 off the wet-dry vacuum that flew through our tester’s gauntlet of spilled cereal and dried maple syrup, and an efficient German vacuum squeegee.