I don’t know why I didn’t notice it before. I guess I trusted that a field labeled as “Cost/conv.” was a simple arithmetic calculation where they divided the cost by the number of conversions. But Google is fudging cost/conversion stats and I think they need to fix it.

### When Did It Start?

Below is a screenshot of an campaign that has been running (with conversion tracking) since 2007. If you do the math yourself, you notice that cost/conversion is calculated correctly from 2007-2010.

However, in the year 2011 Google starts fudging the numbers. How much?

- 2011 – Reported Cost/Conv. = $26.94
- 2011 – Calculated Cost/Conv. = $27.35
- 2011 – Invisible Spend = $42,449.99
- 2012 – Reported Cost/Conv. = $25.04
- 2012 – Calculated Cost/Conv. = $25.97
- 2012 – Invisible Spend = $109,427.18
- 2013 – Reported Cost/Conv. = $23.04
- 2013 – Calculated Cost/Conv. = $25.13
- 2013 – Invisible Spend = $55,929.56

As you can see, this is not a “small” problem. For this campaign alone it is tens of thousands of dollars of spend that seems to just disappear. And the problem is getting worse over time. Google is ignoring more and more spend as time goes on.

I was a little miffed and sent out a tweet:

Anyone ever double checked the cost/conversion data displaying in @AdWords interface & find it's calculated wrong? #ppcchat

— Robert Brady (@robert_brady) July 26, 2013

Which elicited a response from the official @AdWords handle:

@robert_brady Adwords actually doesn't count cost generated by clicks where we can't track the cookies… http://t.co/GRX5ZLCxVq -Andy

— Google AdWords (@adwords) July 26, 2013

Following the link over to the Cue Blog I found an interesting theory. Basically the author states that clicks received on devices without cookies are disregarded. Plausible yes, but I had a hard time imagining how Google could justify ignoring only clicks where it couldn’t track the conversion. That would be effectively “cooking the books” on cost/conversion, which is one of the most important KPIs.

I reached out to the Google reps on this account and they explicitly told me that the the above theory was incorrect and they had a “specialist team” looking into it. I will update you when I get a response, but this is a simple question. Why isn’t Cost/conv. a calculated field where cost is divided by the number of conversions? Seems simple, yet the longer I don’t have an answer the more I wonder; Is Google fudging the stats on purpose?