JavaScript Capabilities by Browser

If I want statistics for the market share for various browsers, I can get them from places like Net Applications or W3Schools (with different collectors skewed in a different directions for various reasons not relevant to this post). Wikipedia has a pretty helpful roundup of the various statistics collectors.

Similarly, if I want statistics for users with JavaScript enabled/disabled, there are several sources, such as and, again, W3Schools.

I’m particularly interested, though, in a combination of those two sets of statistics. What percentage of users disables JavaScript for a given browser? Are Firefox users more likely to have JavaScript disabled than Internet Explorer users? Are IE6 users more likely to have it disabled than those that have upgraded to IE7?

Do you know where I might find these statistics? If so, please let me (and the world, for that matter) know.