Amazon sold 18 per cent more items worldwide during Wednesdays Prime Day promotion than during last years Black Friday.

This is the first time Amazon has held a Prime Day, which offered exclusive offers to members of its Prime service for 24 hours.

Compared to the same day last year, orders increased by 266 per cent. The retailer shifted an average 398 items every second, hitting a total 34.4m sales across the day.

Individual promoted items also saw huge boosts. Amazon sold 14,000 iRobot Roomba 595 vacuum cleaners, compared to a single unit the previous Wednesday, and 41,000 Bose headphones, up from eight a week earlier.

Given the steep discounts, its unlikely to be have been an especially profitable day for Amazon, but the promotion was successful in driving Prime membership. Hundreds of thousands of people signed up to the service, more than any other day since Prime launched in 2005.

“Going into this, we werent sure whether Prime Day would be a one-time thing or if it would become an annual event,” said Greg Greeley, Vice President, Amazon Prime. “After yesterday’s results, well definitely be doing this again.”

And it wasnt just Amazon which benefitted from the promotion, according to data from performance marketing firm HookLogic. Other retailers in HookLogics network saw their traffic nearly double during the day, peaking with a 2.5x spike at 7am EST.