Answer:
This is a difficult question to answer, it really depends who you class as a Jew.
according to the halakha a person's Jewishness is determined on the maternal side. although some people who are Jewish on their paternal side might concider themselves Jewish.
according to some statistics there are about 13 million Jews around the world as opposed to the proposed 17-18 million before world war II
which makes the percent of Jews around 0.2-0.18