Is non-Orthodox Judaism really dying?
It is an oft-repeated trope in the American Jewish community that non-Orthodox Judaism is dying out because of high rates of assimilation among non-Orthodox Jews. As a data scientist, I wanted to investigate these claims using real data.
For this post, I used real data from the 2020 Pew survey of American Jews. That survey contained some interesting information about the retention rates of the various Jewish movements. To understand how the various Jewish movements are growing or shrinking, we need to combine retention rates with birth rates, because the different Jewish movements have very different birth rates. This will allow us to project how the different movements will grow or shrink in the future. I owe some of the basics of this analysis to someone in a Jewish Facebook (“Jewbook”) group.
Currently, Jewish adults are 9% Orthodox, 17% Conservative, 37% Reform, and 36% no denomination/other denomination. The fertility rates of the different Jewish movements are also variable, however. The Orthodox have by far the highest birth rate currently, with 3.3 births per adult. Conservative Jews have a birth rate of 1.8, Reform 1.4, and unaffiliated 1.1. This is an overall fertility rate of 1.517.
From these numbers, you can calculate what percent of births currently are each denomination.
3.3*0.09/1.517 = 0.20
1.8*0.17/1.517 = 0.20
1.4*0.37/1.517 = 0.34
1.1*0.36/1.517 = 0.26
That means that currently, 20% of births are Orthodox, 20% are Conservative, 34% are Reform, and 26% are unaffiliated/other.
To make this easier to conceptualize, we can think of 1000 Jewish people born.
200 are Orthodox
200 are Conservative
340 are Reform
260 are not affiliated
However, we now need to factor in retention and denominational switching. This gives how many of each denomination we will have at the end of this group of Jews’ lifetimes. The Orthodox have a relatively high retention rate and a high birth rate, but very few Jews of other denominations become Orthodox. Conservative have a fairly low retention rate but a somewhat higher birth rate, and some Jews of other denominations become Conservative. Reform have a relatively high retention rate, and many Jews of other denominations become Reform.
200 x .67= 134 O who remain O
200 x .02 = 4 C who become O
340 x .01 = 3.4 R who become O
260 x .01 = 2.6 U who become O
Total=144 Orthodox per 1000 Jews
200 x .10= 20 O who become C
200 x .41 = 82 C who remain C
340 x .04 = 13.6 R who become C
260 x .07 = 18.2 U who become C
Total = 134 Conservative per 1000 Jews
200 x .10 = 20 O who become R
200 x .30 = 60 C who become R
340 x .66 = 224.4 R who remain R
260 x .10 = 26 U who become R
Total = 330 Reform per 1000 Jews
200 x .06 = 12 O who become U
200 x .15 = 30 C who become U
340 x .14 = 47.6 R who become U
260 x .56 = 145.6 U who remain U
Total = 235 Unaffiliated per 1000 Jews
200 x .01 = 2 O who become Ot
200 x .03 = 6 C who become Ot
340 x .03 = 10.2 R who become Ot
260 x .05 = 13 U who become Ot
Total = 31 Other branch per 1000 Jews
200 x .06 = 12 O who become N
200 x .07 = 14 C who become N
340 x .12 = 40.8 R who become N
260 x .21 = 54.6 U who become N
Total = 121 Non-Jewish per 1000 Jews
So therefore, for every 1000 Jews born today, in adulthood, ultimately 14% will be Orthodox, 13% will be Conservative, 33% will be Reform, 24% will be unaffiliated, 3% will be another branch, and 12% will be non-Jewish (roughly).
Then we analyze only the number of Jews who remain Jewish.
Orthodox: 0.14/(0.14+0.13+0.33+0.24+0.03) = 0.161 (16.1%)
Conservative: 0.13/(0.14+0.13+0.33+0.24+0.03) =0.155 (14.9%)
Reform: 0.33/(0.14+0.13+0.33+0.24+0.03) = 0.379 (37.9%)
Unaffiliated: 0.24/(0.14+0.13+0.33+0.24+0.03) = 0.276 (27.6%)
Other branch: 0.03/(0.14+0.13+0.33+0.24+0.03) = 0.0344 (3.4%)
The percentage of Orthodox will increase based on their high birth rate, but maybe not as much as expected because of attrition and very few Jews of other denominations joining. The percentage of Conservative will decrease slightly because of their high rate of attrition, but slightly countered by their relatively high birth rate. The percentage of Reform will slightly increase, despite their slightly lower than average birth rate, because many Jews of other denominations join the Reform movement. The percentage of unaffiliated will decrease significantly because of their low birth rate and because many unaffiliated Jews become non-Jewish.
One should also take into account the number of people who convert to Judaism and what movements they join. According to the Pew study, 10% of Jewish adults today were not raised Jewish in any way but had Jewish parent(s), and 5% had no Jewish background. It’s unclear how to incorporate this into the data and there is not great data on it, but it should counteract at least somewhat the number of Jews who leave Judaism completely.
In conclusion — non-Orthodox Judaism (especially Reform Judaism) is definitely not shrinking and is growing, although Orthodox Judaism is also growing! It is really the proportion of unaffiliated Jews that is shrinking significantly.
If you have any comments on this analysis, please get in touch.