First trillion-dollar public company

The first publicly traded company to achieve a market capitalization of more than $1 trillion is Apple (USA), which exceeded this milestone valuation during trading on the on 2 August 2018.

Apple's share price was boosted by news of strong sales for the iPhone X and, in the longer term, a program of stock buybacks by the company itself.

Chinese energy company PetroChina arguably claimed this record first, briefly hitting a reported market capitalization of $1.1 trillion on 5 Nov 2007. However, this figure was the result of analysts extrapolating a market capitalization estimate from the price of the 4 billion "A shares" that had been offered on the Shanghai Stock Exchange that day, which added up to only a 2.18% stake in the firm.

At the time of the $1.1 trillion reported valuation, the largest stake in the firm (158 billion shares, or 86.29% of the company) was privately held by PetroChina's state-owned parent company, the China National Petroleum Corporation, while the remaining 11.52% (21 billion shares) was being traded as "H shares" on the Hong Kong Stock Exchange (or packaged into groups of 100 for sale as American Depositary Shares on the NYSE) at a much lower price. As a result, the share price for the Shanghai IPO is not representative of the market capitalization of the company as a whole.