Prime Day has grown bigger than just Amazon

Four years ago, Amazon held its first Prime Day, offering steep discounts and deals on its site. Since then, not only has Prime Day ballooned to a two-day affair, it has also gotten much bigger than Amazon.

Why it matters: Per new research from Adobe Analytics, Amazon's competitors will see revenue jump by 79% on Monday and Tuesday, this year's Prime Days. That's the strongest-ever projected bump.

The big picture: The halo effect of Prime Day highlights Amazon's influence on the entire retail market. What started as an Amazon invention has become a Black Friday for July, with Walmart and Target adding their own summer deal days.

• Prime Day has also become a moment for Amazon employees to stage protests. Last year, warehouse workers in Europe rallied against low wages. This year, Minnesota workers are planning a walkout.

Worth noting: The buying sprees that occur during these big sales are accompanied by a subsequent binge of returns, Adobe Analytics notes. Last year, Prime Day purchases saw 30% higher rates of return than goods bought on other days.

Go deeper ... An e-commerce pitfall: never-ending returns