Highest share value

On 22 February 2000, the intraday high price of a single share in the internet service provider Yahoo! Japan (USA/JPN) hit ¥167,899,136 ($1,507,280; £942,989) on the JASDAQ stock exchange. It had closed at a record high of ¥163,000,320 ($1,469,320; £917,692) the previous day.

The main driver behind the record-setting price was the out-of-control market optimism that characterised the Dot-Com bubble of the early 2000s. Yahoo! Japan's previous quarter's earnings (announced on 14 Jan 2000) had only been ¥589 million ($5,548,750; £3,370,150), but forecasters confidently predicted exponential growth in the coming years.

The other factor was the limited supply of shares in the company. Softbank (JPN) owned a 51% stake and Yahoo! (USA) owned 34%. This meant that only 15% of the company was being traded on the stock market, increasing the competition for the available shares.

The shortage of stock was further compounded by the small number of actual shares that this 15% stake was divided into. Usually companies split their shares (so one share becomes two shares with each having half the original's value) when their market valuation gets too high, but Yahoo! Japan's share price had risen so quickly that the stock splits couldn't come fast enough to keep up with demand. This meant that on the day of the all-time high, there were only 4,200 shares being traded on the open market.

Yahoo has since undergone several rounds of stock splits, meaning that a single share represents a much smaller stake in the company than it did in 2000. If there had been as many shares in Yahoo! Japan in 2000 as there are now, the 21 Feb closing price would have peaked at ¥795 ($7.16; £4.47) per share – which is not vastly more than the ¥330 ($2.91, £2.22) Yahoo! Japan's shares were trading for as of 7 Nov 2018.

This sky-high market valuation caused some unexpected side-effects. It briefly made Masayoshi Son (the founder and CEO of Softbank) the second-richest man in the world, and got Yahoo! USA into trouble with financial regulators. As Yahoo!'s minority stake in Yahoo! Japan was worth more than the rest of the company's assets put together, Yahoo! was technically a investment mutual fund according to SEC rules.