D. V. Hinkley, On the Ratio of Two Correlated Normal Random Variables, Biometrika, Vol. 56, No. 3 (Dec., 1969), pp. 635-639 ...

The properties of a measure of dependence q' between two random variables are studied. It is shown (Sections 3-5) that q' under fairly general conditions has an asymptotically normal distribution and ...

If your average weekly sales are $2000, for instance, two adjacent weeks showing sales of $1,900 and $2,100 are more probable than weeks of $0 and $4,000.