Editing Economic calculation problem (section)

=== Equilibrium ===
Allin Cottrell, [[Paul Cockshott]] and Greg Michaelson argued that the contention that finding a true economic equilibrium is not just hard but impossible for a central planner applies equally well to a market system. As any [[universal Turing machine]] can do what any other Turing machine can, a central calculator in principle has no advantage over a system of dispersed calculators, i.e. a market, or vice versa.<ref>{{cite book|last1=Cottrell|first1=Allin|last2=Cockshott|first2=Paul|last3=Michaelson|first3=Greg|year=2007|title=Is Economic Planning Hypercomputational? The Argument from Cantor Diagonalisation|url=http://www.macs.hw.ac.uk/~greg/publications/ccm.IJUC07.pdf|publisher=International Journal of Unconventional Computing|access-date=13 March 2008}}</ref>

In some economic models, finding an equilibrium is hard, and finding an [[Arrow–Debreu model|Arrow–Debreu equilibrium]] is [[PPAD (complexity)|PPAD-complete]]. If the market can find an equilibrium in polynomial time, then the equivalence above can be used to prove that P=PPAD. This line of argument thus attempts to show that any claim to impossibility must necessarily involve a [[local knowledge problem]], because the planning system is no less capable than the market if given full information.

[[Don Lavoie]] makes a local knowledge argument by taking this implication in reverse. The market socialists pointed out the formal similarity between the neoclassical model of [[General equilibrium theory|Walrasian general equilibrium]] and that of market socialism which simply replace the Walrasian auctioneer with a planning board. According to Lavoie, this emphasizes the shortcomings of the model. By relying on this formal similarity, the market socialists must adopt the simplifying assumptions of the model. The model assumes that various sorts of information are given to the auctioneer or planning board. However, if not coordinated by a capital market, this information exists in a fundamentally [[Distributed knowledge|distributed]] form, which would be difficult to utilize on the planners' part. If the planners decided to utilize the information, it would immediately become stale and relatively useless, unless reality somehow imitated the changeless monotony of the equilibrium model. The existence and usability of this information depends on its creation and situation within a [[Price discovery|distributed discovery procedure]].<ref>{{cite book|last=Lavoie|first=Don|title=Rivalry and central planning: the socialist calculation debate reconsidered|date=1985|publisher=Cambridge University Press|isbn=0-521-26449-9|location=Cambridge, UK|oclc=11113886}}</ref>