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Cowles Foundation Discussion Papers

2001

Blackwell’s theorem

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Full-Text Articles in Social and Behavioral Sciences

Measurability Is Not About Information, Juan Dubra, Federico Echenique Mar 2001

Measurability Is Not About Information, Juan Dubra, Federico Echenique

Cowles Foundation Discussion Papers

We comment on the relation between models of information based on signals/partitions, and those based on sigma-algebras. We show that more informative signals need not generate finer sigma-algebras, hence that Blackwell’s theorem fails if information is modeled as sigma-algebras. The reason is that the sigma-algebra generated by a partition does not contain all the events that can be known from the information provided by the signal. We also show that there is a non-conventional sigma-algebra that can be associated to a signal which does preserve its information content. Further, expectations and conditional expectations may depend on the choice of sigma-algebra …


Monotone Preferences Over Information, Juan Dubra, Federico Echenique Mar 2001

Monotone Preferences Over Information, Juan Dubra, Federico Echenique

Cowles Foundation Discussion Papers

We consider preference relations over information that are monotone: more information is preferred to less. We prove that, if a preference relation on information about an uncountable set of states of nature is monotone, then it is not representable by a utility function.