After years of secrecy on how much cut Google takes from publisher revenue earned through Google Adsense the company has finally let the cat out by officially announcing the revenue share figures, in a bid for greater transparency with AdSense publishers - Google revealed that it pays 68% of the revenue that it collects from advertisers to AdSense for content publishers and 51% to AdSense for search partners.

Here is the official post announcing this :

Today, in the spirit of greater transparency with AdSense publishers, we’re sharing the revenue shares for our two main AdSense products — AdSense for content and AdSense for search.

As you may already know, AdSense is comprised of several products. The most popular are AdSense for content, which allows publishers to generate revenue from ads placed alongside web content, and AdSense for search, which allows publishers to place a custom Google search engine on their site and generate revenue from ads shown next to search results. Since AdSense for content and AdSense for search offer publishers different services, the revenue shared with publishers differs for each of these products.

AdSense for content publishers, who make up the vast majority of our AdSense publishers, earn a 68% revenue share worldwide. This means we pay 68% of the revenue that we collect from advertisers for AdSense for content ads that appear on your sites. The remaining portion that we keep reflects Google's costs for our continued investment in AdSense — including the development of new technologies, products and features that help maximize the earnings you generate from these ads. It also reflects the costs we incur in building products and features that enable our AdWords advertisers to serve ads on our AdSense partner sites. Since launching AdSense for content in 2003, this revenue share has never changed.

We pay our AdSense for search partners a 51% revenue share, worldwide, for the search ads that appear through their implementations. As with AdSense for content, the proportion of revenue that we keep reflects our costs, including the significant expense, research and development involved in building and enhancing our core search and AdWords technologies. The AdSense for search revenue share has remained the same since 2005, when we increased it.

We also offer additional AdSense products including AdSense for mobile applications, AdSense for feeds, and AdSense for games. We aren’t disclosing the revenue shares for these products at this time because they’re quickly evolving, and we're still learning about the costs associated with supporting them. Revenue shares for these products can vary from product to product since our costs in building and maintaining these products can vary significantly. Additionally, the revenue shares for AdSense for content and AdSense for search also can vary for major online publishers with whom we negotiate individual contracts.

Of course, we can’t guarantee that the revenue share will never change (our costs may change significantly, for example), but we don’t have any current plans to do so for any AdSense product. Over the next few months we’ll begin showing the revenue shares for AdSense for content and AdSense for search right in the AdSense interface.

We hope this additional transparency helps you gain more insight into your business partnership with Google. We believe our revenue share is very competitive, and the vast number of advertisers who compete to appear on AdSense sites helps to ensure that you’re earning the most from every ad impression. Additionally, when considering different monetization options, we encourage you to focus on the total revenue generated from your site, rather than just revenue share, which can be misleading. For example, you would receive $68 with AdSense for content for $100 worth of advertising that appeared on your site. If another ad network offers an 80% revenue share, but is only able to collect $50 from ads served on your site, you would earn $40. In this case, a higher revenue share wouldn’t make up for the lower revenue yield of the other ad network.

We’re continually working on helping you improve the returns from your site while giving you more control and insight into AdSense. For example, we continue to improve our technology so that we can deliver even better matched ads and attract even more advertisers to your websites. Additionally, we recently began providing more granular ways to find and review the ads on your site, as well as the ability to filter more ads by category. We’re also focused on finding other ways to make AdSense better for you. As you may remember, last December, we asked for your ideas and feedback on how we can make AdSense better. We received more than 600 suggestions and 35,000 votes, and we’ve been reviewing them all.