> A decade ago, economists at eBay, including a former professor of economics at UC Berkeley, proposed an experiment to see how effective the company’s marketing was. All eBay search ads on Google were stopped for three months in a third of the US. There was only a small difference in sales. The economists concluded that the people clicking on search ads were the ones already planning to buy something on the site. eBay was wasting millions of dollars. Other companies may come to similar conclusions. Airbnb slashed its digital marketing budget last year in response to the pandemic and says that it saw no change in online traffic. ...<p>> The dirtiest secret about targeted advertising could be that it doesn’t work.