At the college level, the NCAA issues an annual report on sports sponsorship, participation, and squad size. Their most recent report contains detailed information by gender and division for the period from 1982 through 2007. Since the early to mid 90s, the number of schools sponsoring women’s lacrosse has grown sharply and has surpassed the number for men. For men’s lacrosse, the bulk of the growth has occurred in Division III, while for women’s lacrosse, both Division I and (especially) Division III have enjoyed sharp growth rates.
See the full report, which has numerous graphs that depict the trends for sponsorship, participation, and squad size. There is also a link to a PDF file that has tables for men and women, by division and overall, with the relevant numbers.