The fourth paragraph of the article:

"To provide a consistent snapshot of the top Money Makers' earnings power, we focused exclusively on U.S. income sources, ranking artists based upon how much each of them earned in 2011 from a variety of income streams, including touring, recorded-music sales, publishing royalties and payments from an array of digital services. Our calculations were based on each artist's U.S. net earnings, not gross revenue. Due to a lack of sufficient data, our figures do not include revenue from sponsorships, merchandise sales or synchronization deals."