It's not 85-93% not responding, but 85-93% responding with crap that took some effort to produce. Also if you're actually interested in the position, you're going to be doing more than an hours work (if that's what you want to call it) in the interview process. Lastly, it would be work if I were tricking people into doing something I used as R&D or actual production end-product. This exercise simply establishes qualification.
Lately these are contract positions, and being in a corporate environment here I'm dealing with an agency that deals with other agencies. I still do some direct (usually by Craigslist ad) recruiting. I only submit the screening task to people who have already responded to the position posting. Very few people, maybe 5-7% do not complete the task, and I assume they found another position in the interim.
