Not an expert on the subject but I am sure when it comes to reform judaism this is incorrect. Reform judaism started in the late 1700s and the numbers grew sig

Not an expert on the subject but I am sure when it comes to reform judaism this is incorrect. Reform judaism started in the late 1700s and the numbers grew significantly until relatively recently. Having 2-3 kids among reform Jews was the norm. The reason for the decrease in the number of reform jews (if there is one) is not because of a decrease in birthrate, but is instead because of the massive amount of intermarriage and the reason for the intermarriage is because in the West there has been a decrease in anti-semitism over the past 50-60 years (although anti-semitism has been trending upwards over the past few years).