We are not talking Basque-like numbers. But between 1978 and 1995, 353.766 Poles’ blood types have been added into a database that shows an overall frequency of 19.67%.According to Blood Type Frequencies by Country including the Rh Factor, this would make Poland the nation with the highest proven frequency of rh negatives followed by Brazil and Australia.See the study:The blood type frequencies in the population of Poland Access the PDF directly: https://www.rhesusnegative.net/staynegative/wp-content/uploads/2020/05/poland.pdf