The Nikkei 225 was the Japanese stock-market index whose peak preceded the country’s long asset-price collapse.
The Nikkei 225 reached its historical closing high of 38,915.87 on December 29, 1989. The peak came after a major bubble in Japanese equities and real estate, supported by easy credit and strong optimism about Japan’s economy.
After the bubble began to deflate, Japanese share and land prices fell for years. The prolonged economic stagnation that followed is often called the Lost Decade, although the effects extended beyond the 1990s.
The TOPIX is another important Japanese index and is a common source of confusion. The question refers specifically to the Nikkei 225, a price-weighted index of 225 companies listed on the Tokyo Stock Exchange’s Prime Market.