He's doing it wrong, if you look at the impressions he's got adwords set so that if a keyword is doing well it gets more impressions. That's the wrong way to do this set, you have to configure it to give each keyword equal coverage.<p>Otherwise what happens is that by pure randomness some of your keywords are going to get less clicks than others, and as soon as that happens to one of your keywords they get "frozen" (i.e. they get no more ad impressions so they get stuck at their "random" low value).