Hoarding as a human behavior falls in to two main categories. One type of hoarding is triggered as a response to perceived or predicted shortages of specific goods. Compulsive hoarding, on the other hand, is a mental disorder marked by an obsessive need to acquire and keep things, even if the items are worthless, hazardous, or unsanitary. The compulsive collection and ownership of pets is known as animal hoarding. Compulsive hoarding is thought to fall along the spectrum of obsessive-compulsive disorders.
Hoarding behavior may be a common response to fear, whether fear of imminent society-wide danger or simple fear of a shortage of some good. Civil unrest or natural disaster may lead people to collect foodstuffs, water, gasoline, and other essentials which they believe, rightly or wrongly, will soon be in short supply. Unlike hoarding immediately before or in the wake of a crisis, hoarding a resource while its supply is abundant can actually alleviate future shortages because those who stockpile in this manner will not contribute to future demand when supplies are reduced.
Humans also hoard money, especially if they expect deflation, in which falling prices mean that the purchasing power of money will rise. More generally, money hoarding is the accumulation of money by people who avoid spending it or investing it in economic projects, because of a risk aversion, or of a preference for liquidity, or of a lack of a better use for the money.
Hoarding of goods can often cause the very shortage which has been feared, and governments sometimes choose to introduce rationing in order to combat hoarding, as well as to reduce consumption and waste. However, those who have successfully hoarded the desired goods will not have to worry about the shortage, whether it was their fault or not.
On a larger scale, hoarding can be a business strategy similar to monopolization, where an individual or organization attempts to temporarily control all available supplies of a given good in order to artificially increase the price. This strategy is also known as “cornering the market“.