To be eligible for CNBC's rankings, a person or entity must be the majority owner of at least one sports team valued at $1 billion or more and hold additional sports-related investments worth at least $500 million. Liberty Media, for example, is excluded from the list, despite owning Formula One, because it spun off MLB's Atlanta Braves.

CNBC's valuations include only sports-related assets. For instance, the $12 billion valuation for AEG excludes its music and hotel businesses.

A sports empire is defined by its scale. To determine the enterprise values of these empires, CNBC did not simply total the value of individual sports assets. Instead, CNBC applied a multiple — ranging from 1.1 to 1.4 — to the sum of the assets. The multiple used depended on the teams and other sports properties owned. In some cases, it was also adjusted to reflect recent transactions, such as the limited-interest sale of the San Francisco 49ers.

For NFL, NBA, MLB, NHL and soccer teams, CNBC used its own official valuation rankings. For other sports teams and businesses, it relied on input from owners and executives, sports bankers and public filings.

In cases in which CNBC could not verify reports from people representing the empires it valued, CNBC made informed estimates based on comparable transactions.