FTSE 100 Index 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 FTSE 100 Index — also called FTSE 100, FTSE, or, informally, the "footsie" (pronounced /ˈfʊtsiː/) — is a share index of the 100 most highly capitalised UK companies listed on the London Stock Exchange. The index began on 3 January 1984 with a base level of 1000; the highest value reached to date is 6950.6, on 30 December 1999.
It is the most widely used of the FTSE Group's indices, and is frequently reported (e.g. on UK news bulletins) as a measure of business prosperity.
Wikipedia: Dot-Com Bubble
Wikipedia: FTSE 100 Index