Hanke has also written extensively on the subject of hyperinflation, which occurs when a country's inflation rate exceeds 50% per month. In 2008, Hanke and Alex Kwok published a paper, which estimated that Zimbabwe's hyperinflation peaked in November 2008 at %. This makes Zimbabwe's hyperinflation the second-highest in history – peaking 3.5 months after the Mugabe government stopped reporting inflation statistics, and 1.5 months after the IMF's last estimate of Zimbabwe's inflation rate, with a peak inflation rate 30 million times higher than the last official rate.