My passenger-side headlight was showing a good amount of yellowing. The driver-side headlight was more recently replaced (about two years ago), so it looked fine to me. To remedy this lopsided hue distrubution, I tried the "Sylvania Headlight Restoration Kit" because of Consumer Reports' recommendation. I forgot to take a "before" picture (tragedy), but below is a picture of the car a year ago. You can see that the passenger-side headlight was considerably more cloudy, and the intervening year definitely added to the cloudiness and yellowing.