Both of my grandmothers are from Silesia. One from the Polish, one from the German side. Now that the frequencies of rh negative Poles has been shown to be 19.67% based on data collected between 1978 and 1995, it only makes sense to look at Silesian frequencies. And not to much surprise… they are high. And they have been going down. It shows mixing with outsiders and with that increasing frequencies in the outsiders.
Variability in the frequency of ABO and Rh blood groups in Lower Silesia (Poland): the role of natural selection and genetic drift