> What makes other commodities amenable to having futures, but not onions?
Nothing (at least for other perishable foodstuff); law often doesn't even in theory have a broad universal theory behind it, but instead responds narrowly to observed or perceived immediate problems.
> The fact that futures markets are so heavily regulated, precisely because of the market failures described above, should aid in understanding why markets do not "predict", they "determine". Have you ever wondered why trading onion futures has been banned since the 50s?
You're saying the answer to the above question is "because there was an immediate problem with onion futures in the 50s". I don't think that's what they meant. That would be unrelated to "the fact that futures markets are so heavily regulated".
I guess if everyone has a different opinion, and every reply comes from a different person, there's no "discussion" as I understand it.
Nothing (at least for other perishable foodstuff); law often doesn't even in theory have a broad universal theory behind it, but instead responds narrowly to observed or perceived immediate problems.