You seem to be talking about long term underproduction. In the Irish case, the subsistence farmers would have been devastated by a US overproduction even befor

You seem to be talking about long term underproduction. In the Irish case, the subsistence farmers would have been devastated by a US overproduction even before a famine, similar to subsistence farmers in Africa and India today. Holodomor includes perpetual mismanagement and a political decision not to accept food help or really do anything. No amount of overproduction before Stalin would have prevented food being seized and then rotting in transit. Certainly it's the case that you need at least enough overproduction to drive prices down marginally and to restock a reserve if it is actually used, and make speculation not a sure bet.. I think current subsidies go beyond that and arguably don't work because all that overproduction drove innovations in making food fungible to energy (i.e. as ethenol) and energy is now a more retainable wealth as the major input to proof of work.