[kyrieeschaton]

You can consider "hyperinflation" as a consensus that the government is lying about the value of its currency. How does a consensus develop that someone is lying? It's a complex process, and doesn't have a neatly aggregatable answer.

This is incidentally why Sargent considers the end of hyperinflation to be coincident with a regime change - a liar cannot become credible nearly as easily as he can be replaced.