What is the difference between 買い溜め, 買い込む and 買い占める

Question

I recently encountered 買い込む in the following sentence:

災害に備えて大量の水を買い込んだ。- I bought large quantities of water to prepare for disasters. (pretty straightforward)

Searching through similar words I came across 買い溜め and 買い占める which supposedly mean the same thing (stock up; buy in large quantity etc.) I 've also seen the later being used in expressions regarding COVID-19 such as:

買い占めを自粛してください。- Please refrain from panic-buying.

From what I've understood so far 買い占める means to buy a thing as much as possible, whereas 買い溜め means the same with the addition of some underlying fear and uncertainty(product might be sold out or the price may rise). If that's the case, wouldn't 買い溜め make more sense in the above sentence? Where does it differ from 買い込む.

It would be nice if you could provide some additional example sentences to outline the differences, if there are any.

Answer 1

買い込む is the most neutral of the three. It simply refers to the act of buying something in large quantities for future use. It may be for normal consumption and the stock may last only for a few days.

買い溜め is usually used in this noun form, although the verb form 買い溜める is also possible. It refers to the act of buying something in large quantities and keeping it in stock for some future event, such as a supply shortage, a price rise, and an emergency. 溜める means “to store” or “to save”.

買い占め (noun) or 買い占める (verb) has connotations of buying something in more than fair amounts and at the expense of other buyers when the thing is in short supply. 占める means “to occupy” and the same Chinese character is used in such words as 独占 (monopoly) and 寡占 (oligopoly). 買い溜め, on the other hand, has no such connotation per se. I think this is the reason behind the choice of 買い占め for “panic-buying”.

Unlike 買い溜め, 買い占め has no sense of keeping the purchased items in stock, although they may remain unused for some time.