Can you tell me what's the return on investment from your advertising spending? Don't be shy, if the answer is no, as a consolation I can tell you you are not alone. Stuart Elliott today on the New York Times writes about a recent research commissioned by the Association of National Advertisers, that found out most of marketers are not able to forecast the impact on sales of their marketing investments. There are plenty of data to collect, but apparently people haven't the right models to figure out what those numbers mean.