Nikkei 225 Index

The Nikkei 225 is an index calculated by the Japanese media company Nikkei Inc., made up of shares selected from those traded on the Prime market of the Tokyo Stock Exchange. The index has been published since 1950; this long series makes it possible to trace the Japanese economy's path from the postwar period to today through its stock market.

Like the Dow Jones, the Nikkei 225 uses a price-weighted structure, so companies with higher share prices have more influence on the index. As a result, some companies can have a greater effect than their size would suggest. The other main benchmark in Japan, weighted by company value, is TOPIX; following the two indices together reveals different aspects of the market.

The value of the yen also matters for the Nikkei: a weak yen can enlarge exporters' overseas earnings in yen terms, while a strong yen can have the opposite effect. The Bank of Japan's policies are also closely watched. The Nikkei value on Lzzo.com is in points and is based on Yahoo Finance data.