You want to find empirical studies that show free trade to be harmful to free-trading nations?  No problem; you can find them.  You want to find empirical studies that show government stimulus spending to be a sure-cure for what ails a slumping economy?  There are plenty of such data-rich studies out there.  You want to find empirical studies that show that violent crimes aren’t deterred by the death penalty?  Not a problem.  You want to find empirical evidence that increased rates of handgun ownership increase citizens’ likelihood of dying of gunshot wounds?  Many such studies are available.

You can also find plenty of empirical studies showing the opposite of what is shown by all of the above studies.  And these other studies are, as a group, no less carefully done than are the studies that they contradict.  And these other studies, also, are done by scholars no less credentialed and no less objective than are those scholars who produce the contrary findings.

That’s the reality of the social sciences.  It’s not an exercise in simple observation of simple and self-defining facts, only one or two of which change at any time.

via Where Are My Data?!.