I mean a sharp, unexpected deflation as it actually happens in the real world. In the real world, deflation starts with either a collapsing debt or asset bubble

I mean a sharp, unexpected deflation as it actually happens in the real world. In the real world, deflation starts with either a collapsing debt or asset bubble. Bank runs wipe out deposits, a housing bubble bursts, the stock market crashes, etc. Suddenly people realize they are not as rich as they thought they were. A university endowment realizes it has just fallen by 20%. So everyone cuts spending. The easiest thing to cut is stuff like buying cars or designing new buildings or new construction projects. So when the endowments fell, two-thirds of the architects in Boston got laid off, because the construction projects all stalled and there was no work for them to do. Autoworkers got laid off because people held off on buying cars. Etc. etc.