Pew report. In 2006, 48 percent of Americans said they got their news "from time to time" rather than at "regular times." Today, it's up to 57 percent.
An increase in mobile media is largely driving this grazing habit. It's so easy to check your iPhone or digital device, to make yourself feel informed, in a hurry, on the go, staring at that itty bitty screen. How informed one actually is from such grazing is hard to predict, but hopefully some aggressive scholar out there will attack this question. My guess is, grazing leads to superficial current events knowledge but not deep understanding of the issues. But that's just a guess.