Microsoft became the first public company valued at more than US$500 billion.
Microsoft passed the $500 billion market-capitalization level in 1999 during the peak of the dot-com era. Its Windows operating system dominated personal computers, while Microsoft Office had become a standard productivity suite for businesses and households. Investor expectations pushed the company’s share price to extraordinary levels before the technology bubble burst.
The company was founded in 1975 after Bill Gates and Paul Allen developed and licensed a version of BASIC for the Altair 8800. Its agreement to provide an operating system for IBM-compatible personal computers helped establish MS-DOS and later Windows as central software platforms.
Market capitalization is not the same as a company’s annual revenue or physical assets. It is the market value of outstanding shares, so it can rise or fall rapidly as investors change their expectations. Microsoft’s 1999 milestone occurred during a period of unusually high technology valuations, and the company’s share price later declined substantially after the bubble collapsed.