The differences in estimates stem from different methods used for estimating and the amounts of evidence available to the researchers. The Soviet figures relied on the most crude methodology, also used to make Auschwitz estimates—it was assumed that the number of victims more or less corresponded to the crematoria capacities. Later researchers tried to take much more evidence into account, using records of deportations, contemporaneous population censuses, and recovered Nazi records. Hilberg's 1961 estimate, using these records, aligns closely with Kranz's report.