Apple's share of the U.S. market was up from 35 percent in the fourth quarter of 2012, the NPD data released on Thursday reveals. Rival Samsung was up as well, but not by as much, growing from 22 percent of U.S. smartphones a year prior.
The figures show that Apple's lead in its home market is widening, and that it and Samsung are taking an increasingly larger share of the U.S. market as rivals slip. Together, Samsung and Apple command 68 percent of smartphones owned in the U.S.
Together, Apple and Samsung represent 68 percent of smartphones in the U.S., while 60 percent of mobile subscribers now have a smartphone.
As Apple and Samsung grew, significant losses were seen by competing smartphone makers Motorola, HTC and BLackBerry. The only other company among the top six to see any share gains was LG, which grew slightly but still controls less than 10 percent of the market.
NPD also found that smartphone penetration continues to grow in America, reaching six in ten cell phone users in the fourth quarter of 2013. That was up from 52 percent of the mobile market in the fourth quarter of 2012.
Unsurprisingly, mobile data use is also on the rise, with smartphone owners polled using an average of 6.6 gigabytes per month as of the end of 2013 --?up from 5.5 gigabytes a year prior. NPD cited streaming music services as a "key driver" in data use, with Pandora, iHeart Radio and Spotify taking the top three spots.
NPD's list of the top domestic music streaming services made no mention of Apple's iTunes Radio, which launched last September and is built in to the company's iOS 7 mobile operating system.