# Why were Leah and Bilhah's tribes larger than Rachel and Zilpah's?

I plotted the census results given in Bamidbar, and it struck me that the tribes descended from Rachel are very small. In contrast, those descended from Leah have population counts between average and very large. (Levites are an exception, being a very small tribe descended from Leah, but they are explicitly set apart as not to be counted with the other tribes.)

Initially I thought it was simply a matter of timing: Ephraim and Manasseh are from a generation later, and Benjamin was born late. So their tribes have had less time to grow. But this doesn't work: if it were true, Leah's younger sons Issachar and Zevulun would have smaller tribes than Reuven, but that's not the case.

Then I thought it might have to do with Leah's merit. But then I'd expect the same pattern for the handmaids. Instead, it's reversed: tribes descended from Bilhah are larger than those descended from Zilpah.

Plotting the average tribe count for each matriarch shows that the gap between the smaller and larger groups is more than the standard error. If the tribe of Levi is included, the standard deviation for Leah increases and the two groups barely overlap.

Total counts of descendants are mostly driven by the number of children: 48% of everyone descends from Leah. (50% if the tribe of Levi is included.) The other groups have similar populations, which makes sense since each is descended from two sons. (Joseph has many descendants split between the two tribes, but Benjamin has few.)

Overall, these plots suggest there's a specific pattern and not simply random variance. Is there a reason for this?

• What are the totals? – Al Berko Jun 16 at 12:56
• Between any 4 groups, don't you expect some differences? Are those differences statistically significant? – Al Berko Jun 16 at 12:57
• @AlBerko Thanks, added total and average plots. The difference is bigger than the standard deviation, so this suggests a cause, especially since there's very little randomness in the Torah. But I'd certainly accept "no, there's no particular reason: <such-and-such source> would surely mention one if it existed, but doesn't" as an answer. – Leopold Jun 16 at 13:49
• So Leah stands out because she originated 6 tribes. BTW, after the exile of the 10 tribes, we have probably 90% Yehuda (Leah), 5% Binyomin and 5% Levi. I would also take one step back and ask what those numbers represent in the first place? – Al Berko Jun 16 at 13:54
• Some thoughts: (1) Some members of Ephraim left Egypt early and were killed by the Philistines, so that would have depressed their numbers. (Maybe, even, smaller groups from Menashe and Binyomin went with them too?) (2) Ephraim and Menashe were given a blessing that they will "multiply like fish in the midst of the land" - where one explanation is that it means that they'll multiply specifically in Eretz Yisroel - and in fact we find those tribes complaining to Yehoshua that they're large and that the land assigned to them isn't large enough (Yehoshua 17:14-18). – Meir Jun 17 at 17:33