Why is the Jewish world population very small?

Answer 1

Well, it should be Why ARE there so few Jews in the world?

Judaism (the religion) is not widespread and is originated from the Middle East, and is practiced particularly in Israel. Judaism's background's are of "the chosen people" etc. not giving much motivation or welcoming for "gentiles" or non-Jews to the religion, whereas religions such as Buddhism and Christianity are widely accepting and welcoming of just about everyone.

Also, I assume the Holocaust played a role in downsizing the population of the Jews, but the main factor is of the nature of the religion.

Answer 2

There are several reasons. The three most important are:

1. Jews don't proselytize or attempt in any way to get people to convert to Judaism. There are no Jewish missionaries. As a result, the religion really only grows vertically (i.e. reproduction) not horizontally.
2. Jews have been consistently repressed or second-class citizens in all countries where they lived with the exception of modern Western states since the 1960s and the United States since the 1910s. It was never physically advantageous to be Jewish and many left the faith to avoid the persecution. And breakaway groups such as the early idolaters, Sadducees and Karaites, tended to eventually mix into the non-Jewish population.
3. Hitler murdered one-third of world Jewry in the Final Solution and other Jew-murdering mechanisms (such as the Einsatzgruppen). The Holocaust resulted in a large decrease in the total Jewish population, especially since a good portion of those murdered were the Hasidim who have a relatively high birth-rate. (It is believed that had the Holocaust not occurred, there would be 23 million Jews in the world today instead of 14 million. In addition to the Holocaust, hundreds of thousands of Jews died in the First Destruction, the Second Destruction, and the Spanish expulsion; and tens of thousands in other persecutions such as the Crusades.

Answer 3

Repeated murder and oppression. When the Romans crushed the Jewish revolts in the first and second centuries, they killed huge numbers of Jewish civilians as well as most of the Jewish armies. During the Crusades, roughly 1/4 of the Jewish population of Europe was slaughtered, as well as a good fraction of the Jews then in Palestine. During the Black Plague, Jews were repeatedly slaughtered when they were blamed for the plague. When Jews were expelled from countries, large numbers of fleeing refugees died as they searched for new homes. When Russia began intense persecution of Jews in the late 19th century, a leader estimated that 1/3 would convert to Christianity, 1/3 would die, and 1/3 would flee. The Holocaust in the 20th century was outstanding for its slaughter, but not without precedent.

And, as that Russian noble said, whenever persecution has been severe, some Jews left Judaism in order to save their lives.