>>>so google applique smart pricing on my website ?
>>>Two years ago, 4000 visits would have equaled about...
Whoa, please back up and read what incredibill posted. Earnings have less to do with the amount of visitors to your site. Smart pricing is not something that robs you of earnings you should have earned. Erase both those concepts from your thoughts. Amount of visitors to your site is not really a determining factor of potential income. It's not about traffic. There are other more important factors.
Here is the deal: Go out and learn about affiliate marketing. Here is some of what you need to know to make affiliate marketing (and AdSense) work for you:
1. Understand how much various niches pay. You can only understand this by looking at the payouts per action. You can get an idea by reviewing how many ads appear on the SERPs for various keyword phrases, but it's a good idea to familiarize yourself with the payout for each action.
2. Get an idea of the amount of competition there is per click. More competition means less payout.
3. Here is the BIG one that anyone who wants to earn with AdSense needs to know: Understand what keywords fit into the buy cycle of the Internet consumer, understand the content context that cultivates site visitors that are in the buy cycle.
4. Read this post to learn how to earn more with AdSense
[webmasterworld.com] more details.