PetroChina briefly became the world’s most valuable company by market capitalization during its 2007 stock-market debut.
PetroChina shares began trading in Shanghai in November 2007, and the stock surged on its first day. The resulting calculation gave the company a market capitalization above $1 trillion, briefly placing it ahead of ExxonMobil at the top of global public markets.
The valuation was controversial because PetroChina had a relatively small publicly traded portion compared with the state-owned portion. Market capitalization still counts the implied value of all shares, including shares not freely traded, which helps explain how a company could reach such a figure despite limited public float.
The share price soon fell sharply from its debut peak. The episode illustrates why market-cap rankings can change rapidly and why an intraday valuation is not the same as a durable leadership position.