system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: In a situation of constant hyperinflation (eg prices doubling every few days), how do individual shopkeepers know when to raise prices by how much?
gpt
In most cases when this actually happens or is close to happening, the answer is "they don't". Many will stop producing (because presumably raw material costs are also doubling) and no one wants the wages paid in a currency that buys less every day. 

1. People start to barter trade.
2. More frequently, they only accept foreign currency that is more stable. 

The problem is that the price charged has to account for the increased price of new supplies plus compensation for the buying power lost in the intervening period (as income to the owner). Ultimately this is self defeating, since higher prices drives even higher prices which is why hyperinflation is destructive. The economy simply breaks down as trade fails. People try to exchange their money for goods (leading to hoarding) and the luckier ones exchange for foreign assets and currencies.