Largest pre-Kinsey study group

The largest pre-Kinsey study - which just preceded the first Kinsey report -was "The Sex Life of Unmarried Men" (1947) by L. B. Hohman and Bertram Schaffner, based on interviews with 4,600 selective service selectees at military induction centres in New York State and Baltimore.
The study was remarkable for its finding that only three or four inductees per thousand reported homosexual experience. However, the Kinsey group later pointed out that "three-to-five-minute interviews .. . held in army induction centres were not conducive to winning admissions of socially taboo behaviour."
Ref: L. B. Hohman and Bertram Schaffner, "The Sex Life of Unmarried Men" (1947), American Journal of Sociology, Volume 52 Number 6 (May 1947): 501-507.