Science must find for every effect a single cause. The historian is rarely faced with the same requirement.Historians have the advantage of being able to live with explanatory ambiguity that would be unacceptable in science.

Frame of reference has been manipulatedCrime statistics are often manipulated for political purposes by comparing to a year when crime was very high. This can expressed either as a change (down 60% since 2004) or via an index (40, where 2004 = 100). In either of these cases, 2004 may or may not be an appropriate year for comparison. It could have been an unusually high crime year.This also happens when comparing places. If I want to make one country look bad, I simply express the data about it relative to whichever country which is doing the best.This problem tends to crop up in subjects where people have a strong confirmation bias. (“Just as I thought, crime is up!”) Whenever possible try comparing rates from several different starting points to see how the numbers shift. And whatever you do, don’t use this technique yourself to make a point you think is important. That’s inexcusable.