Gary Gutting interviews Daniel Hausman in the NYT's The Stone (image Robert Streiffer):
Daniel Hausman: Speaking of predictive power can be misleading. Scientists (and I include economists) are not fortunetellers. Their theories only allow them to predict what will happen if initial conditions are satisfied. Elementary physics enables us to predict how long it will take an object to fall to the ground, provided that gravity is the only force acting on the object. Predicting how long it will take a leaf falling from a tree to reach the ground or where it will land is a much harder problem.
In John Stuart Mill’s view, which I believe is basically correct, economics is a separate and inexact science. It is separate from the other social sciences, because it focuses on only a small number of the causal factors that influence social phenomena. It is inexact because the phenomena with which it deals are influenced by many other causes than the few it focuses on.