The cross-country comparative approach provides a number of unique advantages over national studies: It can exploit institutional variation that does not exist within countries; draw
on much larger variation than
usually available within any country; reveal whether any result is country - specific or more general; test whether effects are systematically heterogeneous in different settings; circumvent selection
issues that plague within - country identification by using system - level aggregated measures; and uncover general - equilibrium effects that often elude studies in a
single country.
I'm not sure pissing off the people who do still go to the comic book store every week and drop a lot of money
on single issues even though trades are
usually more cost - effective is the way to go about it, though.