Media Life: In just a few years, smartphones have gone from extravagance to necessity. For the first time, more than three quarters of Americans own these gadgets, and adoption continues to grow at a very rapid rate. As of fourth-quarter 2014, 77% of Americans owned smartphones, according to a new study from Nielsen that looked at smartphone ownership in the United States. That’s a sharp jump from fourth quarter 2013, when smartphone ownership was 69 percent.