https://techcrunch.com/2019/06/27/250-retailers-will-compete-against-amazons-prime-day-up-from-194-last-year/

Amazon’s Prime Day event, now in its fifth year, is no longer just a big sales day for Amazon — it’s become the official kickoff to back-to-school shopping season and a new sales holiday that extends across the web among rival retailers. And those retailers’ competitive response to Prime Day is bigger than ever this year, according to a new report from RetailMeNot. In 2019, the firm estimates that 250 retailers will take part in Prime Day by offering deals of their own. That’s up from 194 last year, and up from just 7 retailers on Amazon’s first Prime Day in 2015.

The increased participation may be related in part to the size of Amazon’s sale this year. Prime Day has been stretched out over the years. In 2018, for example, Prime Day became a 36-hour sale and, at the time, the biggest shopping event in Amazon’s history.