Mammele: What’s your concern about the math? Suppose today the age gap (or whatever the multitudes of causes) results in 5% of girls being unable to get married due to their being a shortage of unmarried men, if the rabbonim permit 5% of girls to be a second wife, that would greatly alleviate the problem of those girls who otherwise were r”l doomed to have been unable to find someone to marry. If the percentage is 10%, then 10% could be allowed to become a sister-wife. On either of those two examples it would mean 95% or 90% of the people would still have “traditional” one-husband/one-wife relationships.
Now I’m not suggesting that this is a quick-fix that will overnight resolve the shiddduch crisis. Or that, even, the percentages of plural wives families will automatically equal the exact percentages of girls who are short a husband. But certainly it will go part of the way, or hopefully even a long way, towards helping resolve the shiddduch crisis we are experiencing regarding an imbalance of boys and girls in the market. Even a partial fix is better than none.
And as stated, this solution will need to be highly regulated by the rabbonim shlita to ensure its success both in terms of who is capable of participating in it as well as to regulate its occurrence/frequency remain in hand. But as I stated, I think there will be more of an issue of finding enough people willing and capable of participating (even though only a small percentage is needed in the first place) than a problem of having too many willing participants. But even a smaller than needed participation rate will go a long way in helping resolve the crisis.
And, again, I stress I’m not advocating a hefker velt in this or that this program be started by any Yankel or Mirel on their own. It first needs the haskama of gedolei yisroel before it can get off the ground (no one has the right to do it on their own beforehand). Even the NASI program of encouraging close in age shidduchim got the signed haskama of gedolei yisroel first. As noted the Sefardim have been doing this for centuries until very recent times and some Teimanim still have plural wives even today. I don’t think any of the children will be discriminated or feel second-class or even feel differently than other children. Children of divorced families manage in a frum world of mostly married parents.
And there have been rabbonim in the past who suggested the possibility of the current rabbonim ending the cherem is a real and serious possibility if the circumstances were right. I believe the Gra is one of the rabbonim and I know that on one of his easily available Torah tapes that Rav Avigdor Miller suggested the rabbonim could do so.