text: You have to be careful. Strong correlation does not necessarily prove a causal connection. I remember a letter to the London Times in the 1970's where a Cambridge undegraduate took a leading economist to task. The economist had found a strong correlation between the amount of money in circulation and inflation, he concluded that a large amount of money in circulation caused inflation. The undergraduate found a higher correlation between the incidence of dissentry in Scotland and inflation. He claimed therefore that dissentry was the cause of inflation. What they both had found was two increasing series of numbers. Unless you can explain the mechanism by which the two series are contected then proced with your hypothesis with caution. Don't bet your last dollar until you see whether your predictor works for a reasonable time, and then be cautious because unless you can explain the conection the circumstances may very well have changed since you original data was collected