“Assuming the proportion of male to female births is close to 50% among all Jews, why do you think the numbers differ between chassidim and misnagdin?”
Silly question. As Reb Yosef has previously noted, he is open to relaxing cherem R’ Gershon such that an ehrliche yid could have 2 or 3 wives. Clearly without even addressing the Litvish vs. Chassidish complications the current pool of eligible bnos yisroel is inadequate to support the polygamous lifestyle to which he aspires (absent a substantial number of bochurim changing their preferred pronouns).