Which speculative bubble’s collapse caused the main Japanese stock-market crash beginning in 1990?

The collapse of the Japanese asset price bubble caused the main Japanese stock-market crash that began in 1990.

During the late 1980s, Japanese stock and land prices rose to exceptionally high levels. Easy credit, financial liberalization, optimistic expectations, and rapid lending helped push valuations far beyond sustainable levels. The Nikkei 225 reached its historical peak of 38,957.44 on December 29, 1989.

The Bank of Japan tightened monetary policy, and asset prices began to fall. The Nikkei continued declining through the early 1990s, while land prices also weakened. Banks were left with large quantities of non-performing loans backed by depreciating collateral, damaging credit creation and economic growth.

The resulting period is commonly called the Lost Decade, although economic weakness and financial repair extended beyond the 1990s. The episode is often compared with later bubbles because it shows how stock prices, property values, leverage, and banking problems can reinforce one another after a boom reverses.