Notes

[1] Actually it's hard to say now. As Jeremy Seigel points out, if the value of a stock is its future earnings, you can't tell if it was overvalued till you see what the earnings turn out to be. While certain famous Internet stocks were almost certainly overvalued in 1999, it is still hard to say for sure whether, e.g., the Nasdaq index was.

Seigel, Jeremy J. "What Is an Asset Price Bubble? An Operational Definition." European Financial Management, 9:1, 2003.

[2] The number of users comes from a 6/03 Nielsen study quoted on Google's site. (You'd think they'd have something more recent.) The revenue estimate is based on revenues of $1.35 billion for the first half of 2004, as reported in their IPO filing.

Thanks to Chris Anderson, Trevor Blackwell, Sarah Harlin, Jessica Livingston, and Robert Morris for reading drafts of this.