Click figure to enlarge.
Here are a couple simple graphs using Google Trends to show web searches for the term “concealed carry.” After each of these three terrorist attacks over the last 90 days, you can see a sudden increase in interest for concealed carry. With each attack, the size of the increase in interest has gotten larger.
This interest in concealed carry obviously translates into more concealed handgun permits.
— Demand for CCW permits surge following San Bernardino Attack (KABC-TV Los Angeles)
— Concealed carry licenses rise after CA shooting (KCTV-TV San Antonio, Texas)
Here is a similar figure since 2004 and it clearly shows that the previous big increase in interest in concealed carry occurred in December 2012, right after the Newtown attack.
Some claim that Obama’s executive orders issued on January 6th, 2016 were responsible for some of the increase. For example, “Indiana gun sales on the rise in wake of terrorist attacks, Obama’s executive orders.” But this claim isn’t based on daily data and the monthly data can make it very difficult to disentangle the different effects. Using the daily Google trend data makes it hard to see much impact from Obama’s executive orders.