I have read stories of Jews who tried desperately to get out of Germany before the war started. Some made it, and some were heart breakingly close before the door slammed shut.
Many Jews got out of Germany quite easily. German Jews were generally well off and Germany didn’t start real persecution until four years after the Nazis took over.
In contrast, eastern European Jews were generally poor and the Nazi started rounding them up right after conquering these countries.
In Germany, 64% of Jews survived. In Poland, it was just 9%.
http://www.historyplace.com/worldwar2/holocaust/h-statistics.htm