What started with the Influenza outbreak in 2008, search discovery made available by Google revealed how Influenza outbreak correlate to searches for flu-related terms with Google Flu Trends. Google search data tools, Google Trends and Google Insights, were not designed with such research capabilities in mind.
Internet researchers needed a system more like Google Trends but in reverse functionality, they wanted to enter some real world activities and be able to see which search terms best match the trend. In response to the researchers quest, came the launch of Google Correlate in mid 2011.
Google Correlate allows search patterns to be compared against a specific time series (weekly/monthly), or against U.S. states. It mines similar patterns in search data terms. The new search tool does not yet support international application, however, users can upload their own data set and map it against Google's search terms.
The most unique feature in the new search tool is the ability to approximate data points from a data set based on graphs. Google Correlate is able to find data set which map closely to a given graph. You draw a time series and Google Correlate find terms that best match the trend.
Google, however, is fast to point-out that correlation is different from causation both in the FAQ and explanatory note.
