How much did the Jewish population decrease after World War II?

The Nazis rounded up Jews and sent them to special camps where they were killed.

The European Jewish population in 1950 was 3.5 million people in contrast to the 1933 European Jewish population of 9.5 million people (a difference of 6 million people whence the 6 million number comes). 2 million of the 3.5 million remaining Jews were in the Soviet Union.