In the previous parts we’ve learned how to evaluate and optimize our ad monetization efforts. We will cover several gotchas and things you should pay attention to while setting up and managing your ad monetization strategy.

Does your ad provider disregard the fill rate while calculating eCPM?

We’ve already discussed that different ad providers may deliver different fill rates for different types of apps and audiences. The question is how do they report it to you?

Let’s say you login to your ad provider’s client area and see a report that looks like this:

Impressions	Clicks	CPC	eCPM
1,000	10	$0.1	$1

This looks fine on the surface, but what does “Impressions” mean in this case? If you only have this one measure in your report and don’t have fill rate or the number of ad requests to compliment it, mostly likely it means that the ad network calculated the eCPM based only on the ads they actually delivered and disregarded all requests that returned empty-handed.

On the other hand your report may look like this:

Requests	Impressions	Clicks	CPC	eCPM
2,000	1,000	10	$0.1	$0.5

As you can see the ad network honestly reports that it was able to fulfill only 50% of your ad requests and calculates your eCPM based on that.

Obviously, if you compare two ad providers and don’t pay attention to the method they use to calculate eCPM, you will choose the first network because the eCPM looks 2 times better. In reality, though, it’s quite possible that the second one actually delivers better results. For all we know the first one may have a fill rate of 10% or even less.

It is incorrect to directly compare eCPM for different ad types

Ad networks like to display impressive eCPM numbers on their websites to lure publishers. But if you blindly compare these numbers (even if they are absolutely honest) you are probably not getting the whole picture.

If one ad network promises $5 eCPM but only runs interstitial ads and another network claims $1 eCPM on banners, which one do you choose? From a purely commercial point of view the answer comes down to your ability to show more than 5 banners (say during game play) in a timespan when you would display 1 interstitial (say after each level). If you can do this the “banner network” will actually deliver higher revenues.

Obviously in this particular scenario there’s nothing preventing you from using both of them, but when you start comparing interstitials to video ads, etc., you often have to choose one or the other as your primary network.

Can you control minimum bid?

Some ad providers let you set a minimum accepted bid, meaning that if an advertiser bids less than $X on your user you refuse to show their ads. When an ad network doesn’t allow you to control this you may end up in a situation where an advertiser bids 1 cent for a click and you end up showing their ads, even though you don’t make any meaningful money from such ads. In cases like this you would rather switch to a different ad provider or display your own house ad.