Photo: Ute Grabowsky/Photothek via Getty Images

The internet is kind of a big deal. Since 2000, the world’s favorite series of tubes has grown its number of users by 887 percent. Today there are 3.5 billion users worldwide — or 48 percent of the population — checking out a billion or so websites. But here’s the thing: While the number of sites increases mercilessly, and the number of people getting online continues to grow, human beings only have so much time to spend online. And in the U.S., the amount of attention people pay to the internet depends on how much money they make.

The finding comes in a new working paper published by the National Bureau of Economic Research that was recently highlighted by the economics blog Marginal Revolution. The paper’s authors find that households that make $25,000 to $35,000 a year spend 92 more minutes a week online than households that clear $100,000 a year in income. In an email to Science of Us, lead author and University of California, Davis, economist Andre Boik explained that it’s a function of how inexpensive the internet is compared to other pastimes. “Lower-income households are less likely to have access to the quality of leisure activities [like sports or travel] that higher-income households do, so they are more drawn to the internet because usage is free,” he wrote. Wealth also predict the kinds of sites people visit. The researchers — who also include Shane Greenstein of Harvard Business School and Jeffrey Prince of Indiana University — say that higher-income households tend toward news, games, online banking, shopping, education, sports, and video (looking at you, Netflix). Importantly, the data only include what people look at on a browser on a PC, so non-browser multiplayer video games and alternative devices (smartphones and tablets) aren’t included.

The data come from ComScore, the web-analytics service, which tracked over 40,000 home devices in U.S. households in 2008 and over 30,000 in 2013. The two years provide snapshots of a key time in the internet’s history in the U.S., as broadband exploded from from 62 to 73 million households. The cost of building websites went down thanks to Amazon Web Services and the like. By 2013, half of U.S. households had a smartphone. Streaming got its start with YouTube in 2006 and Hulu and Netflix in 2008, but grew hugely from there — by 2013, video made up 16 percent of internet usage. Facebook only opened its gates to the general population (i.e., moms) in 2006, but by 2013, it took up 26 percent of people’s time online. At the time, overall browser-based internet use dropped between 2008 and 2013, presumably because everyone was sending each other selfies (2013 word of the year!) by then. Unfortunately for anybody in an advertising-driven business, the attention pie only appears to be getting comparatively smaller: According to the study, the number of websites available has nothing to do with how people fit the internet into their lives. It’s a good reminder that the way people spend their time online has less to do with the content, and more to do with the consumer.