The information that I have is that in 1933, there were ~9.5 million jewish people in Europe, and then the jewish death toll was ~6 million. From 1933 till the end of the Holocaust, I would think that at least 10% would have been able to flee west to the Americas, the UK, or even take refuge in Switzerland(~1 million). So really the Nazi's killed 6/8.5 million jewish people. Also, there are the people who were caught by the SS but were lucky enough to survive, which I would guess to be around 5-10% of number of deaths(~450 thousand), which suggests that 6.5/8.5 million people were found by the SS.

So, in an age where computers didn't even exists, and every record was written on paper, how did they manage to identify more than 3/4 Jewish people in an entire continent? How did they get such information about everyones religion?

Thanks in advance