The Online Display Ad Effectiveness Funnel & Carryover: A Meta-study of Predicted Ghost Ad Experiments

We present a meta-study of 432 online display ad field experiments on the Google Display Network. The experiments feature 431 advertisers from varied industries and on average include 4 million users and last 20 days. These experiments employ the Predicted Ghost Ad experimentation methodology. Across experiments, we find median lifts of 16% in site visits and 8% in conversions. We relate the baseline attrition as consumers move down the purchase process — the marketing funnel — to the incremental effect of ads on the consumer purchase process — the ‘ad effectiveness funnel.’ We find that incremental site visitors are less likely to convert than baseline visitors: a 10% lift in site visitors translates into a 5-7% lift in converters. We then examine the carryover effect of the campaigns to determine whether the in-campaign lift carries forward after the campaign or instead only causes users to take an action earlier than they otherwise would have. We find that most campaigns have a modest, positive carryover four weeks after the campaign ended with a further 6% lift in visitors and 16% lift in visits on average, relative to the in-campaign lift.