Did Zimbabwe have an inflation of 89.7 sextillion percent? From a Cato Institute article by Steve Hanke1 (emphasis added):

The Economist’s most recent infraction on Zimbabwe’s hyperinflation appeared in the May 2016 issue. The magazine claimed that the hyperinflation peaked at an annual rate of 500 billion percent. Where did this figure originate? You guessed it. That figure is buried in the IMF’s 2009 Article IV Consultation Staff Report on Zimbabwe.
In reality, Zimbabwe’s annual inflation rate in September 2008 was 471 billion percent, not 500 billion percent. More importantly, Zimbabwe’s hyperinflation peaked in November, not September. It was then that Zimbabwe recorded the second-highest hyperinflation in history: a whopping 89.7 sextillion percent. This is 179 billion times greater than the IMF’s figure.


Did Zimbabwe, at one point, record a hyperinflation of 89.7 sextillion percent? Wikipedia cites the IMF figure.

How did Steve Hanke come up with the number 89.7 sextillion?

Is Steve Hanke's methodology accurate? Reasonable? Trustworthy?

Why are the two numbers so different?


Note: Steve Hanke certainly seems to believe that inflation for some countries is higher than actually reported (e.g. the Zimbabwe article I cited, this tweet regarding Sudan from 9 hours ago, and this tweet regarding Argentina from 11 hours ago). Maybe this could be considered in an answer?
1Professor of Applied Economics and Co-Director of the Institute for Applied Economics, Global Health, and the Study of Business Enterprise at The Johns Hopkins University in Baltimore
The figures you question are from Hanke and Kwok (2009).


According to Hanke and Kwok (2009), yes.
A stock (Old Mutual) was listed on both the London Stock Exchange (in GBP) and the Zimbabwe Stock Exchange (in Zimbabwe dollars). Under the assumptions of price arbitrage and purchasing power parity, one can infer Zimbabwe's inflation rate.
I haven't carefully attempted to replicate their work, but I can see no reason to question Hanke and Kwok's general methodology.
The Economist's figure of 500 billion percent is for Sep 2008. (Hanke and Kwok's estimate for Sep 2008 is 471 billion percent.) The higher figure of 89.7 sextillion percent is Hanke and Kwok's estimate for the month to Nov 14, 2008.


Their Table 1: