My PhD student Charly Andral came with the question of the birthdate of importance sampling. I was under the impression that it had been created at the same time as the plain Monte Carlo method, being essentially the same thing since
hence due to von Neumann or Ulam, but he could not find a reference earlier than a 1949 proceeding publication by Hermann Kahn in a seminar on scientific computation run by IBM. Despite writing a series of Monte Carlo papers in the late 1940’s and 1950’s, Kahn is not well-known in these circles (although mentioned in Fishman’s book), while being popular to some extent for his theorisation of nuclear war escalation and deterence. (I wonder if the concept is developed in some of his earlier 1948 papers. In a 1951 paper with Goertzel, a footnote signals than the approach was called quota sampling in their earlier papers. Charly has actually traced the earliest proposal as being Kahn’s, in a 14 June 1949 RAND preprint, beating Goertzel’s Oak Ridge National Laboratory preprint on quota sampling and importance functions by five days.)
(As a further marginalia, Kahn wrote with T.E. Harris an earlier preprint on Monte Carlo methods in April 1949, the same Harris as in Harris recurrence.)
Xi'an's Og 