Unfortunately, many who have examined the impact of so-called “shall-issue” or “right-to-carry” laws assume that the adoption of such laws causes a large, immediate increase in the number of permits. But that is often not the case, for states differ widely as to how easily permits can be obtained. This problem is particularly problematic for studies that have looked at the period after 2000. In fact, the share of the adult population with permits increased less during the 1999-2010 period in the states that adopted right-to-carry laws than the states that they are being compared against.