The Wilshire 5000 is a bit of a misnomer – it doesn’t actually maintain a list of 5000 stocks that it measures by weighting market capitalization. While only a week old, as a publicly traded company, it’s been announced that Twitter Inc (NYSE:TWTR) will join The Container Store Group Inc. and  Burlington Stores Inc (NYSE:BURL) on the index after the close of trading this Friday.

Twitter

Twitter IPO needs no special accommodation from Wilshire

The index has been around since it was conceived by Dennis Tito in 1974. The same Dennis Tito that became the first “space tourist” when the multimillionaire funded his own trip to the International Space Station in 2001. Tito paid $20 million to make the trip as a 60th birthday gift to himself; he did, however, have to wait until he was 61 years of age before he spent his 7 plus days in space.

“From its inception in 1974, the intent always has been for the Wilshire 5000 Total Market Index to be the most complete and investable measure of the total U.S. equity market,” noted Robert J. Waid, managing director. “As a rules-based index, the Wilshire 5000 does not need to make special accommodations for early entry of large IPOs, like Twitter Inc (NYSE:TWTR), as stock additions always have been made monthly for U.S. companies with readily available price data. The Twitter IPO is no exception.”

Wilshire trading above 18,000

Presently the Wilshire 5000 is trading just above 18,000 and this year marks the first time that number has ever been seen. For a five year period beginning in 2004, the Wilshire 5000 was known as the “Dow Jones Wilshire 5000” when Dow Jones & Company assumed responsibility for both calculation and maintenance. The index returned to Wilshire Associates in March, 2009 and can be tracked by following the ticker symbol W5000.

Wilshire has grown to a firm of more than 300 employees serving the investment needs of institutional clients around the world. Based in Santa Monica, California, Wilshire provides services to clients in more than 20 countries representing more than 500 organizations with assets totaling approximately US $7 trillion as of the end of 2012.

As of this writing Twitter Inc (NYSE:TWTR) was down around 0.4% on the day and is trading at $42.77 with heavy volume.