The Nikkei 225 fell by about 82% from its 1989 peak to its 2009 low.
The index reached an intraday record of 38,957.44 on 29 December 1989, near the end of Japan’s asset-price bubble. Japanese shares and property had become extraordinarily expensive after years of rapid credit growth and speculation.
After the bubble burst, the Nikkei entered a prolonged decline. The index reached an intraday low of 7,054.98 in March 2009 during the global financial crisis. Comparing those two levels gives a fall of roughly 82%, although the exact percentage depends on whether closing or intraday figures are used.
The period is often called Japan’s Lost Decades because weak growth, banking problems, deflation, and repeated financial stresses lasted for many years. The Nikkei’s decline was not a single-day crash; it was a long collapse interrupted by temporary recoveries.