Declines from ATH and Recovering High, from Andre Wallin
Looking at Dow Jones there have been 17 declines from ATHs since 1900 over 22%. Only two have recovered high within 1 year. 1990 and 1998 had declines around 22% and recovered within 1 year. 1917, the year preceding the Spanish flu recovering the all time high took 2 years.