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"Market socialism is a term used to denote two different economic
system(s) based in socialism which operate according to market
principles. The first term relates to an economy directed and guided
by socialist planners on either a local or state level. The earliest
models of this form of market socialism were developed by Enrico
Barone (1908) and Oskar R. Lange (c. 1936).  Lange and Fred M. Taylor
proposed that central planning boards set prices through "trial and
error," making adjustments as shortages and surpluses occurred rather
than relying on a free price mechanism. If there were shortages,
prices would be raised; if there were surpluses, prices would be
lowered."

<http://en.wikipedia.org/wiki/Market_socialism>