The Dow Jones Peaks
Another reason may have been accelerated business spending in preparation for the Y2K switchover.
Once New Year had passed without incident, businesses found themselves with all the equipment they needed for some time, and business spending quickly declined. This correlates quite closely to the peak of U.S. stock markets. The Dow Jones peaked on January 14, 2000 (closed at 11,722.98, with an intra-day peak of 11,750.28 and theoretical peak of 11,908.50) and the broader S&P 500 on March 24, 2000 (closed at 1,527.46, with an intra-day peak of 1,553.11); while, even more dramatically the UK's FTSE 100 Index peaked at 6,950.60 on the last day of trading in 1999 (December 30). Hiring freezes, layoffs, and consolidations followed in several industries, especially in the dot-com sector.
The Dow Jones Industrial Average also referred to as the Industrial Average, the Dow Jones, the Dow 30, or simply as the Dow; is one of several stock market indices, created by Wall Street Journal editor and Dow Jones & Company co-founder Charles Dow. The average is named after Dow and one of his business associates, a statistician, Edward Jones. It is an index that shows how certain large, publicly-owned companies have traded during a standard trading session in the stock market. Dow compiled the index to gauge the performance of the industrial sector within the American economy. However, the performance of the Dow continues to be influenced by not only corporate and economic reports, but also by domestic and foreign political events such as war and terrorism, as well as by natural disasters that could potentially lead to economic harm. It is the second oldest U.S. market index after the Dow Jones Transportation Average, which Dow also created. The average is computed from the Dow Jones Indexes by the stock prices of 30 of the largest and most widely held public companies in the United States. The Industrial portion of the name is largely historical, as many of the modern 30 components have little or nothing to do with traditional heavy industry. The average is price-weighted, and to compensate for the effects of stock splits and other adjustments, it is currently a scaled average. The value of the Dow is not the actual average of the prices of its component stocks, but rather the sum of the component prices divided by a divisor, which changes whenever one of the component stocks has a stock split or stock dividend, so as to generate a consistent value for the index.
Wikipedia: Dot-Com Bubble
Wikipedia: Dow Jones Industrial Average