Zero impressions, more than zero clicks - how/why does this happen?

Is it AdMob or did I mess something up in my app?

The fill rate for Admob interstitial is considered quite low.
You can try out monetizing with other ad network like StartApp, Mobilecore or AppNext.
With StartApp, you can earn another $15 when your impressions hit 100k.
Refer to the following link for more details.

I think there is a bug on AdMobs side the past few days. I have also been experiencing stange behaviour with interstitial impession stats. See