A question from Yahoo! Answers:
Why do economists often disagree?
Because they are not just economists; they are policymakers or advisers to policymakers. Good economics is not necessarily a good policy and is usually far from good politics. So when an economist wears a political hat, he can be tempted to disagree even with himself if there is some political gain from doing so.
Larry Summers, Deputy Secretary of Treasury in the Clinton administration, objected to repeal of estate tax in late 1990s, even though Larry Summers, an economics professor at MIT, did some research in early 1980s that suggested (correctly) that estate tax may be a hindrance to capital formation.
Glenn Hubbard, Chairman of the Council of Economic Advisors in the G.W. Bush administration, insisted that budget deficit is not inflationary, even though Glenn Hubbard, an economics professor at Columbia, wrote a textbook that said (correctly) that budget deficit was in fact inflationary.