The amount of time American children spend watching online videos has increased significantly over the past four years, although overall screen time has changed little, according to research from non-profit Common Sense Media.

Its survey of more than 1,600 8-18-year-olds explored how they use media across an array of activities and devices.

This found that, on average (and excluding any use for school or homework), 8-12 year-olds, or tweens, spent 4 hours 44 minutes on screen media each day; the older age group of 13-18 year old (teens) spent 7 hours 22 minutes.

That was roughly the same as in 2015, the last time Common Sense Media carried out such a survey. But in the intervening period, the balance has shifted towards online videos, with tweens more than doubling the time spent watching these, from 25 to 56 minutes daily; teens followed a similar and only slightly less steep path, from 35 minutes to 59 minutes.

At the same time, the percentage of young people who say they watch online videos every day has doubled for both groups, from 24% to 56% for tweens, and from  from 34% to 69% for teens.

That trend sits alongside a rise in smartphone ownership across all ages: 19% of 8 year-olds now have one, compared to 11% in 2015 and 91% of 18 year-olds have one against 77% in 2015. But the greatest shifts are evident in the middle age band where every year from 11 to 14 has seen an increase in ownership of 20 percentage points or more.

Watching TV/video (53%) and gaming (31%) occupy most of tweens’ screen time. Teens devote less of their screen time to these two activities, 39% and 22% respectively, but spend more time than their younger counterparts on social media (16%) and browsing websites (8%).

“More and more screen time is devoted to content that’s been picked for you by an algorithm,” said Michael Robb, a co-author of the study and senior director of research for Common Sense Media.

“And then there’s more individualized uses of media on a personal device, rather than a family sitting together,” he added in remarks reported by the Washington Post

Sourced from Common Sense Media, Washington post; additional content by WARC staff