We know China is on an insatiable quest to buy up commodities all over the world. A note from Citigroup Inc. helps put things into perspective.

For starters, China and other emerging economies such as South Korea and India are buying up stakes in mines globally, while privatization in China, India and the former Soviet Union is also bringing more assets to the market. According to Citi, in 2004 traditional mining economies including Australia, Canada and South Africa (as well as the U.K., as the go-to destination for mining...