Why Do 2 Similar Sites Have Huge eCPM Differences?

.... what am I missing here?

[austtr]

An old circa 1997 site has been publishing Adsense for a few years with a mix of 300x250 blocks, skyscrapers and leaderboards. Its eCPM, and earnings, remain fairly consistent.

Another site of similar age, similar topic, similar search terms, similar traffic numbers, similar click through numbers... also runs 300x250 blocks, skyscrapers and leaderboards. This second site has been publishing Adsense since Aug 2007.

The eCPM of the second site is only about one-third of the other site and shows no sign of improving. This seems to indicate that Google is placing very low paying publisher ads on this site.

As a webmaster, what do I need to do to encourage Google to start placing higher paying adverts on the second site?

[zett]

similar traffic numbers

Is the traffic quality also similar, i.e. are traffic and clicks coming from the same countries or regions?

There are some (including me) who observed that the regional mix seems to be important for the definition of EPC and eCPM.

[jomaxx]

Also does the traffic for the 2 sites come from the same sources, e.g. Google organic listings or whatever? Even the specific search made is relevant. Some sources work out to be better than others, some regions work out to be better than others, some user demographics work out to be better than others.

You may also want to look at possible differences in the "on-page" factors that Google apparently looks at when doing Smart Pricing. Just because 2 sites have a broadly similar subject doesn't mean Google sees them as equivalent.

[tim222]

The most obvious difference is that the first site has been in the AdSense program for a few years longer than the second. Besides any conspiracy theories that the AdSense algorithm might consider a site's longevity in the program, there's also the fact that the first site has had more time to attract site targeted ads. More advertisers targeting a site should increase the value of its page views and clicks.

[dibbern2]

This is pure speculation, but...

there seems to be a trust factor -rather undefined-- in G's search rankings. Longevity appears to be component. Perhaps a similar mechanism is used in AdSense.