I do not understand the Reform Jews membership numbers:
They say they have 1.5 million members in 900 synagogues. That is an average of 1,700 members per synagogue.
Meanwhile, the Southern Baptists as an example have 17 million members in 41,000 churches or an average of 400 members per church.
The Presbyterian Church USA has an average membership of just over 200 members per church.
It certainly appears the Reformed Jews are grossly exaggerating their importance. Perhaps they only have about 250,000 members.
There is no census or actual membership count. These numbers are based on the "National Jewish Population Survey" which a phone poll of numbers dialed at random and asking the person who answers, "Are you Jewish?" If the answer is "yes" the person is asked questions about the level of observance. Reform estimates its "membership" based on the number of people whose observance is "minimal or none."
In Israel, a country of 5 million Jews, less than 5,000 are members of a Reform temple.