• by Wendy Davis , Staff Writer @wendyndavis, April 2, 2015

Most Americans now have smartphones, but data caps appear to be preventing people from fully using their devices. That's according to a new study by the Pew Research Center.

The report says that 64% of Americans now own a smartphone -- up from 35% just four years ago. Researchers found that nearly one in five Americans, or 19%, say they rely at least at times on a smartphone to access the Web, while 7% of Americans say they rely almost exclusively on smartphones to go online at home -- meaning that they don't have residential broadband.

People who have smartphones, but lack residential broadband, appear to have been hit hard by data caps. Almost one in three -- 30% -- of that group said they “frequently” reach their maximum allotment of data, while 51% say they occasionally do so.

Even people who can access the Web from their homes are running into their data caps, according to the report. Overall, 15% of smartphone users say they “frequently” reach their maximum, while 37% say this happens occasionally.

One reason why people could be maxing out is that they are watching video and listening to music on their phones. Seventy-five percent of smartphone users between the ages of 18 and 29 reported watching video on their devices, while 64% of that group said they listened to music on their phones. Just 31% of smartphone users age 50 and over said they watch video on their phones, while 21% of that age group said they have listened to music or podcast on their phones, according to Pew. The report was based on a December phone survey of 2,002 adults and interviews conducted in October with 2,188 smartphone owners.

The report doesn't delve into different business models used by wireless carriers. But the fact that so many people are hitting data caps suggests that companies that arrange to sponsor data -- that is, to have their data excluded from consumers' caps -- could gain a significant advantage with mobile users.

Whether that type of arrangement will meet with regulatory approval isn't certain.

The Federal Communications Commission's new net neutrality rules don't appear to prevent wireless carriers from subscribers by the byte. Current pay-per-byte billing plans typically involve charging people a monthly fee to use a maximum amount of data -- often 3 GB or 5 GB -- and then imposing extra fees if they exceed that amount.

But the rules contain a “general conduct” provision that broadly prohibits service providers from unreasonably impeding consumers and content providers from reaching each other. The FCC said last month that it will take a “case-by-case approach” to evaluating whether particular practices -- including exemptions from data caps -- violate that general conduct standard.