You can rank companies by many ways, e.g., by profits, stock market value or by revenue (sales in US$). The most common way is to rank companies by revenue because revenue is directly related to market share. Exxon had been #1 oil company in the world for many years in terms of both revenue and profit. Only in the last few years, RD/Shell's revenue passes Exxon, so Exxon is now #2 oil company right after RD/Shell in terms of revenue. However, Exxon remains the most profitable oil company in the world. Hope it keeps that way because I work for XON.