Worth of perfect information in bernoulli bandits

For k-armed Bernoulli bandits with discounting, sharp comparisons are given between average optimal rewards for a gambler and for a .perfectly informed' gambler, over natural collections of prior distributions. Some of these comparisons are proved under general discounting, and others under non-increasing discount sequences. Connections are made between these comparisons and the concept of .regret' in the minimax approach to bandit processes. Identification of extremal cases in the sharp comparisons is emphasized.