Sums, products and ratios for Mckay’s bivariate gamma distribution

Motivated by hydrological applications, we derive the exact distributions of R = X + Y , U = XY and W = X / ( X + Y ) and the corresponding moment properties when X and Y follow McKay’s bivariate gamma distribution. The expressions turn out to involve several special functions. We also provide computer programs for generating tabulations of the percentage points associated with the distributions.