The recruiter is supposed to be on your side, so it makes sense to share this information. I went through a recruiter to get my last two jobs, and was able to secure a 35% and 37.5% increase each time (same recruiter), and she was well aware of my compensation each time. She said that in both cases she was prepared to share it with the companies, but they never ended up asking. I think that if the companies like you enough, they will offer you what you're worth, regardless of what you were making before. And I'm sure they can figure out the number within a reasonable range using Glassdoor and salary.com anyway.