Obama/McCain Ad Number Confusion

Yesterday, comScore released a report on the number of online ad impressions run by Barack Obama’s and John McCain’s presidential campaigns in 2008. As regular readers of ClickZ’s Campaign ’08 section know, we’ve been getting ad impression data among other related info from Nielsen Online’s AdRelevance for months now. I figured I’d delve into previous AdRelevance reports and compare ad impression info from the two. I put together a chart displaying comScore’s and Nielsen’s ad impression data for the last 6 months (below).

Discrepancies? Oh yes.

Now, to be fair, comScore and Nielsen usually don’t see eye-to-eye on anything. So, variations between the two can be expected. However, there are some real whoppers here when it comes to disparities.

Perhaps the most glaring difference is in the June numbers. AdRelevance says the Obama camp ran around 80 million, but ComScore pegged it at around 244 million ad impressions — three times the AdRelevance number. And check out January ’08. AdRelevance said McCain ran 19 million ad impressions, while comScore says it was more like 4.5 million. Confused?

I would be too. Though I’ll continue to report this stuff, the impression numbers truly have to be taken as broad estimates. No matter whose numbers you look at, you’ll find Obama’s campaign is running more Web ads — a lot more. And if you haven’t seen my story today on how much he’s spending on online ads, it hit $5 million sometime around July.