The price of each issue included in the index is weighted by its relative market capitalization. Let:
The index is then calculated as:
One index point corresponds to about US$1 billion. Hence the value of the index, multiplied by one billion dollars, roughly equals the total capitalization of the US stock market. Dow Jones publishes two versions of the index, one based on full market capitalization and another based on a float-adjusted market capitalization, reflecting the number of shares actually available to trade.
The list of issues is updated monthly to add new listings resulting from corporate spin-offs and initial public offerings, and to remove issues which move to the pink sheets or stop trading for ten days or more.
The Wilshire 5000 did not close above its March 24, 2000 peak above 14,000 points (record high of the 20th century) until February 20, 2007, and a hypothetical investment in the Wilshire 5000, made at the 2000 peak and with subsequent dividends reinvested, did not become profitable on a closing basis until October 3, 2006.
On April 20, 2007, the index closed above 15,000 for the first time. On that day, the S&P 500 was still several percentage points below its March 2000 high, because small cap issues absent from the S&P 500 and included in the Wilshire 5000 outperformed the large cap issues that dominate the S&P 500 during the cyclical bull market.
Since late 2007, the expansion of subprime lending difficulties into a wider financial crisis plunged the United States stock market into a bear market that accelerated beginning on Ugly Monday, September 15, 2008. On October 8, the Wilshire 5000 closed below 10,000 for the first time since 2003, and trades near the 9,000 level as of October 9, representing a loss of more than $6.5 trillion in market capitalization since the nominal record highs of 2007.