@Sue22 - Fair enough. According to the 5C newspaper article quoted below, there were 39 drug related referrals from Pitzer - a college commonly ranked among Wesleyan’s peers - to the campus authorities in 2013. Pitzer is approximately one third the size of Wesleyan, meaning, that on a per capita basis the rate of occurrence was very nearly the same.
Moreover, the Pitzer referrals were strictly as a result of ambient complaints of suspicious activity, not from rigorous inspections for contraband. To the contrary, it appears as if the Claremont Colleges - which include Pomona, Harvey Mudd, Claremont McKenna, Pitzer and Scripps - have a far more passive approach toward drug enforcement than Wesleyan:
http://www.tsl.pomona.edu/articles/2013/2/22/feature/3613-drug-policies-prove-difficult-to-enforce