How did Zimbabwe's prices end up doubling about every day in 2008?

Zimbabwe's prices ended up doubling about every day because the government paid its way by printing ever more money while production collapsed, until nobody trusted the currency. Almost all hyperinflations have been caused by government budget deficits financed by creating currency, and Zimbabwe fits that pattern. The Reserve Bank responded to the dwindling value of the dollar by repeatedly arranging to print more banknotes, and from 1999 to 2009 food production and other sectors fell sharply.

How bad was it? Economists usually follow Cagan's description: hyperinflation is when the monthly inflation rate exceeds 50%. The government stopped filing official inflation statistics at the height of it, so economist Steve Hanke estimated the rates himself. His index put the peak, in mid-November 2008, at a monthly rate of 79.6 billion percent, with prices doubling about every 24.7 hours. Even that is largely theoretical, since hyperinflation did not proceed at that rate over a whole year. A $100 trillion banknote could not pay for a simple bus fare.

People lived it in small ways. Minibus fares rose through the day, so the evening ride cost more than the morning one, and the next morning's more still. By late 2008 some ATMs gave a data overflow error, because the sums had so many zeros.

What ended it was not a clever policy but giving up the currency. In April 2009 Zimbabwe stopped printing its dollar and foreign currencies were used instead.