Marketing consultant Interbrand collaborates with Business Week to publish its annual ranking of global brands based on 4,000 valuations conducted over 20 years.

With 34 offices in more than 20 countries around the globe, Interbrand lists international trademarks that have generated the greatest economic returns for their owners.

A criteria for Interbrand's study is that an eligible global brand must achieve at least a third of its sales outside of its home country. Furthermore only publicly traded companies are included, thus excluding a well-known brand like Mars which is privately held. Wal-Mart is excluded because it does business under too many different brand names in various foreign markets.