Google’s Chief Economist Hal Varian and Hyunyoung Choi write on Google’s research blog about using google search queries, such as Google Trends and Google Insights for Search,  to estimate economic activity in Predicting the Present with Google Trends:

Our work to date is summarized in a paper called Predicting the Present with Google Trends. We find that Google Trends data can help improve forecasts of the current level of activity for a number of different economic time series, including automobile sales, home sales, retail sales, and travel behavior.

Even predicting the present is useful, since it may help identify “turning points” in economic time series. If people start doing significantly more searches for “Real Estate Agents” in a certain location, it is tempting to think that house sales might increase in that area in the near future.