The main propagation effect on interference between adjacent earth-space paths is considered to be the differential rain attenuation. In the present paper, a unified method for the prediction of rain differential attenuation statistics, valid for both single/dual polarization systems, which is based on the two-dimensional gamma distribution, in proposed. The method is particularly oriented for application to earth-space paths located in Japan and other locations with similar climatic conditions. From another point of view, the present work is considered to be the complementary aspect of the present work is considered to be the complementary aspect of the predictive analysis which uses the lognormal assumption. Numerical results are presented referring to communication systems suffering from differential rain attenuation under the hypothesis of using both single and dual polarization.