Some executive search firms provide compensation data for in-house counsel. They gather it mostly from candidates, partly from surveys, and sometimes from clients. Since the executive search firms receive as their fee a percentage of the first-years’ compensation of the lawyers they place, the firms would favor higher compensation figures (those comp levels might also induce some lawyers to look around for other jobs, which helps search firms).
Keep in mind, when reviewing the figures search firms release regarding compensation the potential for bias. Ask careful questions about the source of the figures, and compare the figures to other compensation data. You can get law department compensation data from such firms as Abbott Langer, Altman Weil, and Hildebrandt International.