How can you determine objectively, over time, that you are getting any better at producing code?  For example, I may sit here and feel that I know <language> now, and I use <technique> now, so I must be better.  But this does not account for my own bias, or the fact that I may be getting better at a slower rate than intended, or I may actually suck at <technique> and not realize it.  What methods are available for one to objectively rate one's own abilities?  What about to objectively compare them to their peer groups?
What personal milestones can you use to measure growth in your programming abilities?
self improvement;skills;metrics