In my article '"New Political Economies" Then and Now: Economic Theory and
the Mutation of Political Doctrine', Amer. Journ. of Econ. and Soc. 61.1
(2002): 13-51, I attempted to show how purely internal developments in
economic analysis from c. 1870 - 1930 gradually undermined the theoretical
basis of laissez-faire and predisposed most economists to collectivism by
the Second World War. The article is reprinted as Chap 14 in my recent book
(2004). If I may add a comment to this discussion: I do not think 'ideology'
has very much to do with it. Economists trying to understand how the system
works believed -- during the period I refer to here -- that they were
discovering, by politically neutral scholarly inquiry, that many of the
political-economic doctrines they had assimilated as young men from their
elders were scientifically defective.

Anthony Waterman