According to a new study from the Pew Research Center, 1 in 5 Americans say they use the Internet “almost constantly.”

Pew has been tracking how many Americans use the Internet for 20 years, but its most recent survey is the first time respondents have been able to answer “almost constantly” when asked about their Internet use. Previously, respondents could only report that they used the Internet “several times per day.”

Young people are spending the most time online, with 36% of Americans between the ages of 18 and 29 saying they are there almost constantly.

But it’s not just a millennial thing: 28% of Americans between 30 and 49 say they’re constantly online as well.

In general, the more money your household makes, the more likely you are to spend a lot of time on the Internet. In households making $75,000 or more, 28% report going online almost constantly, compared with only 16% of households making under $30,000.

One major factor contributing to the rise in Internet use is that nearly three-quarters of Americans use a mobile device, Pew discovered. When you’ve got a smartphone, the line between being online and not blurs because you have an Internet-connected computer potentially vibrating every few minutes. Among adults who use smartphones or tablets, 87% go online daily, compared with 65% who don’t carry a smartphone with them. A full 27% of smartphone users across all groups say they are online almost constantly.

Across all age groups, 73% of Americans—nearly 3 out of 4 adults—go online on a daily basis.

Pew’s addition of the “almost constantly” response is a logical step considering the remarkable growth of the Internet. The first Pew study to look at online usage suggested only 14% of Americans used the Internet at all in 1995.

The study is sure to raise long-simmering issues over whether smartphones and the Internet are causing increasing distraction and even addiction. If one in five Americans is online “almost constantly,” that puts a lot of adults at risk of developing compulsions to constantly check email or other web notifications.

Overall, although Internet usage is pervasive, some people are still holding out. Pew found 13% of adults said they don’t use the Internet at all.

For more on millennials, watch this Fortune video featuring Deloitte CEO Cathy Engelbert:

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