It turns out that user queries can be very well correlated with, for example, the rate of spread of influenza. That is the demand rate associated with the same flu, may coincide with a growth rate of the number of cases of influenza. If such a correlation is displayed in the chart, then there is almost complete agreement. This phenomenon had been seen in late 2008, when Google developers had started the service Google Flu Trends. This service tracks the number of user requests associated with the flu, and compares these data with the speed of propagation of the disease. It turned out that on the basis of these data, we can predict the probability of occurrence of influenza epidemic in a particular region or even predict the course of the epidemic also for sufficiently long period of time.
Naturally, scientists of various areas were interested of this service, the developers of corporations in a few years introduced a new service that let you track the relationship between the number of certain queries, and arbitrary function that described some kind of trend, given in the form of data / information. By downloading any function describing a process (eg, increase in the number of representatives of the Passeriformes in New Zealand), you can track the relationship of such a function with a certain group of queries.
In addition, the service allows you to manage at all without the input of statistical data, but simply to monitor the frequency of recurrence of any queries of specific group. And another interesting point is that the new service allows you to define queries that correlate with each other.
Sure, the creators of the service does not guarantee a causal relationship between all of these trends. Possibly, variety of events and trends can correlate with each other, for instance, the occurrence of the query associated with football, may correlate with the actual function that describes the change in luminosity of a star. One can only imagine what a fantastic correlation can be carried away by people interested, for example, in esotery. Nevertheless, the service Google Correlate is quite interesting, and, presumably, is useful for the scientists and marketers.