9 months of daily A/B-testing of Google AdSense banner ads on Gwern.net indicates banner ads decrease total traffic substantially, possibly due to spillover effects in reader engagement and resharing.
An attempt at a ARIMA(4,0,1) time-series mixture model implemented in Stan, where the mixture has two components: one component for normal traffic where daily traffic is ~1,000 making up >90% of daily data, and one component for the occasional traffic spike around 10× larger but happening rarely: