One of the surveys I remember the ARRL did, was this one back in 2001 with 4744 respondents : NOVICE SPECTRUM SURVEY DRAWS HEAVY RESPONSE, see ARRL Letter July 2001:
http://www.arrl.org/arrlletter%3Fissue%3D2001-07-20Of course, if one is interested in the number of varied surveys the ARRL has done over the years (excluding the QuickStat stuff), you only need to go to the ARRL web site and put the word "survey" in the Website Search Field.