How to Find Bid Gaps

1. Log in to your Google AdSense account.
2. Click on 'Clicks' to organize your report by the number of ad clicks your site received during the week. Assume, for example, that one ad block received 200 clicks one week and that you earned a total of $20. This puts your CPC -- cost-per-click that you're paid by advertisers -- at $0.10 for that ad block.

3. Compare it to ad blocks that received similar numbers of clicks on the same site, because presumably your site should be running ads in the same niche. Assume the second ad block earned you a total of $15 for 250 clicks. This ad block's CPC is therefore $0.17 per click.
4. Attach another ad block to your page if you have any space left. Wait for it to receive similar traffic over the next week or two and check your rate again. Assume this ad block gave you $10 for 200 clicks, putting you at $0.05 per click.
5. Divide each of these amounts by 0.68 to determine how much the advertiser paid for an ad block. For example, if you get $0.05 per click, the advertiser's bid was $0.07.
6. Compare the amounts to get a general idea of bid gap. Low-paying ad blocks should probably be removed unless they get a high enough click-through rate to compensate for the low profit.