You can be unprofitable at -0.5%. It stabilizes; for a runaway inflation you need to have a positive feedback loop. From the author’s write-up (https://benoitessiambre.com/simcb.html):
>The inverse happens with negative interest rates. If the central bank makes a loss on a loan, people are taxed to make the central bank whole in a kind of reverse seigniorage. Now in the real world this doesn’t tend to happen.
>It's difficult to create hyperinflation in SimCB (unless in the aftermath of high unemployment leading to low market inventory), when you lower interest rates, even to negative rates, the central bank takes a loss and you get reverse seigniorage, people's money is automatically taxed away, which offsets the inflationary effects of low interest rates and the system self stabilizes. This is partially due to there not being government debt to help fuel high inflation. I don't know how well this reflects real world economics.
>The other aspect that is missing from SimCB which could cause hyperinflation is the option for people in an economy to switch to another currency.
>(…) Now I could still have allowed central bank losses in SimCB's model. This might have made sense especially given that SimCB doesn't have a government to amplify central bank moves by borrowing. Central banks taking a loss, instead of taxing reverse seigniorage, might have simulated government stimulus, allowing the negative interests to act as little helicopter drops of money. Real world governments often borrow and spend during conditions that warrant very low rates (or under any other conditions really) to help put money into circulation. Something to try in a future version.
>The inverse happens with negative interest rates. If the central bank makes a loss on a loan, people are taxed to make the central bank whole in a kind of reverse seigniorage. Now in the real world this doesn’t tend to happen.
>It's difficult to create hyperinflation in SimCB (unless in the aftermath of high unemployment leading to low market inventory), when you lower interest rates, even to negative rates, the central bank takes a loss and you get reverse seigniorage, people's money is automatically taxed away, which offsets the inflationary effects of low interest rates and the system self stabilizes. This is partially due to there not being government debt to help fuel high inflation. I don't know how well this reflects real world economics.
>The other aspect that is missing from SimCB which could cause hyperinflation is the option for people in an economy to switch to another currency.
>(…) Now I could still have allowed central bank losses in SimCB's model. This might have made sense especially given that SimCB doesn't have a government to amplify central bank moves by borrowing. Central banks taking a loss, instead of taxing reverse seigniorage, might have simulated government stimulus, allowing the negative interests to act as little helicopter drops of money. Real world governments often borrow and spend during conditions that warrant very low rates (or under any other conditions really) to help put money into circulation. Something to try in a future version.