Thanks for this post! Your effort in outreach is truly unmatched-- and you make a good case for why that might be a good thing. I wonder, though, what you think your turnout would have been if you hadn't done all this outreach. Is it the case that you had a much easier time last year because you were pulling interested members from all years, while this year your potential pool included only first years? 

Also, it's interesting that posters had such a bad turnover rate for mailing list sign-ups but brought in a significant portion of the Intro group. As a poster fan myself, I'd say this could be reason to keep up this low-investment marketing strategy, if only as a visual reminder to those already interested.