This week’s four-day Amazon Prime sale is lifting e-commerce sales at retail sites across the board. It always does, according to Adobe Digital, with consumers anxious to comparison shop, and other retailers launching their own competing online sales events.

And for the first time ever, Adobe said more than half of all online sales this week will come from shopping done on smartphones, a record 52.5%, compared to laptops, desktops and other devices.

Adobe said there are two reasons smartphone shopping is becoming dominant. The first is that, over the past few years, web designers have redesigned e-commerce sites for retailers to better fit the small screen.

“If you remember, there was a time when buying something on a device, everything was very small, image wise and font wise. It was a bit more challenging of an experience versus laptop or desktop,” Adobe Digital Insights Manager Vivek Pandya said.

The second reason consumers are doing more e-commerce shopping on their smartphones is because of the role smartphones play in daily routines. The smartphone fills voids in many people’s daily routines. In other words, it’s easy to kill time on the phone.

“When we think about how the consumer is managing idle time, and in between those moments of experiences where maybe they are a little bored or just trying to stay occupied, the e-commerce experience is faster and easier in those moments,” Pandya said.

Shopping retail websites on smartphones has also proved to lead to significantly more impulse buying because of ease and idle times during which people are shopping.

There might be one other reason for more online shopping on smartphones, more appreciated by older consumers than younger ones. Smartphone screens aren’t tiny anymore.

“They can do the sorts of things that they are used to doing on a laptop or desktop. They can open up multiple browsers, do a lot of comparisons and flip through apps very easily,”  Pandya said.