A common question many publishers ask is why does my ad fill rate drop? The cause of the drop is usually the result of one of the following factors: a decline in advertising demand, change in demographic makeup of users, change in geographic location of users, changes or problems with technology or a change in performance metrics.

The most common cause of a drop in fill rate is due to a decline in advertising demand. Advertising demand is cyclical and tends to be lower at the beginning of each quarter and rise at the end, so it is natural for the fill rate to drop at the beginning. Advertisers are constantly starting and ending campaigns, so when one campaigns ends the amount of ads available may drop resulting in a lower fill rate.

Many advertising campaigns target specific demographics and if there is a change in the demographic makeup of the users of a publisher’s site or app, it can result in a lower fill rate. This typically does not happen quickly but gradually over time, sometimes due to a new audience being introduced to a site or app. This new audience could be users from a different country which can result in very different user demographics.

Some advertising campaigns are targeted to specific geographic areas, and if the geo location of the users changes or a new campaign begins that is restricted to certain areas, the fill rate can be affected. Typically advertisers will try to match up their geo targeted campaigns with publishers who have traffic in those regions but this is not always possible.

Technological breakdowns or changes can have a significant impact on fill rate. The breakdowns can occur at several points: the publisher’s website or app may stop working preventing ads from being delivered, the publisher’s ad server may stop working or the advertiser may have a breakdown preventing them from delivering ads to publishers. There are numerous technological reasons that could prevent an ad from being delivered and displayed, and we are not going to cover all of them but be aware that it is one of the most common causes why a fill rate drops.

In addition to technological breakdowns, changes in technology are also a common cause of a lower fill rate. The changes can include releasing a new version of a website or app, changing to a new ad server, changing to a new video player, releasing changes to the logic of the ad server or technology changes on the advertiser’s side. Identifying the exact cause of a lower fill rate due to introducing new ad serving components can be difficult to track down, but if you notice a lower fill rate, corresponding with the introduction of some new component, you should begin your investigation there.

The last common cause for a drop in fill rate is a change in publisher performance metrics. These metrics include the click through rate (CTR) and view through rate (CTR). Some advertisers allocate campaigns based on performance metrics, and they have certain target metrics they are looking for. If a publisher has been running a campaign for awhile and the metrics are not meeting the advertiser’s target, then they may remove the campaign from running on that publisher which could impact their fill rate.

Determining why a publisher’s fill rate drops is not always easy to identify but there are several common areas to investigate. When looking into the cause of the drop it is always helpful to share as much information as possible (ie we changed ad server, we released a new version of our app, etc.) with the advertiser to help track down the cause. Withholding information will only make the process more difficult and can extend how long it takes to resolve it. Ultimately, it is in the best interest of both the publisher and advertiser to identify the cause of the low fill rate and try and improve it so both sides can potentially make more revenue.