Growth in "constitutional carry"
From Charles Cooke, in the National Review Online:
"In 1990, some form of "constitutional carry" obtained in just 0.25 percent of the geographical area of the United States, and for only 0.22 percent of the population. Today, those numbers are 42 percent and 18 percent, respectively."
And, as he notes, those numbers are likely to grow appreciably in 2017.