One of the early proponents of advertising, John Wanamaker, is famous for saying “Half the money I spend on advertising is wasted, the trouble is I don’t know which half”. Even though he made this statement all the way back in the 19th century, and despite all the advances in technology since then, it has been hard to measure the effectiveness of advertising. This is particularly the case where there is a cross-over from the digital world to the physical world. For example, a dentist may use pay-per-click ads to generate more traffic to their website and more calls to their practice. In a competitive location, the cost of a click can be high and the monthly cost for a campaign can easily run into the thousands. Despite this spend, the dentist can’t easily track how many calls and appointments all this advertising is generating for their practice and it can be even more difficult to calculate what their return on investment is.