The search engines' market shares vary from market to market, as does competition. In 2003, Danny Sullivan stated that Google represented about 75% of all searches.[42] In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.[43] As of 2006, Google held about 40% of the market in the United States, but Google had an 85-90% market share in Germany.[44] While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.[44]
In Russia the situation is reversed. Local search engine Yandex controls 50% of the paid advertising revenue, while Google has less than 9%.[45] In China, Baidu continues to lead in market share, although Google has been gaining share as of 2007.[46]
Successful search optimization for international markets may require professional translation of web pages, registration of a domain name with a top level domain in the target market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are essentially the same, regardless of language.[44]