Esperanto speakers are more numerous in Europe and East Asia than in the Americas, Africa, and Oceania, and more numerous in urban than in rural areas. Esperanto is particularly prevalent in the northern and eastern countries of Europe; in China, Korea, Japan, and Iran within Asia; in Brazil, Argentina, and Mexico in the Americas; and in Togo in Africa.
An estimate of the number of Esperanto speakers was made by the late Sidney S. Culbert, a retired psychology professor at the University of Washington and a longtime Esperantist, who tracked down and tested Esperanto speakers in sample areas in dozens of countries over a period of twenty years. Culbert concluded that between one and two million people speak Esperanto at Foreign Service Level 3, "professionally proficient" (able to communicate moderately complex ideas without hesitation, and to follow speeches, radio broadcasts, etc.). Culbert's estimate was not made for Esperanto alone, but formed part of his listing of estimates for all languages of over 1 million speakers, published annually in the World Almanac and Book of Facts. Culbert's most detailed account of his methodology is found in a 1989 letter to David Wolff . Since Culbert never published detailed intermediate results for particular countries and regions, it is difficult to independently gauge the accuracy of his results.
In the Almanac, his estimates for numbers of language speakers were rounded to the nearest million, thus the number for Esperanto speakers is shown as 2 million. This latter figure appears in Ethnologue . Assuming that this figure is accurate, that means that about 0.03% of the world's population speaks the language. This falls short of Zamenhof's goal of a universal language, but it represents a level of popularity unmatched by any other constructed language.
Marcus Sikosek has challenged this figure of 1.6 million as exaggerated. Sikosek estimated that even if Esperanto speakers were evenly distributed, assuming one million Esperanto speakers worldwide would lead one to expect about 180 in the city of Cologne. Sikosek finds only 30 fluent speakers in that city, and similarly smaller than expected figures in several other places thought to have a larger-than-average concentration of Esperanto speakers. He also notes that there are a total of about 20,000 members of the various Esperanto organizations (other estimates are higher). Though there are undoubtedly many Esperanto speakers who are not members of any Esperanto organization, he thinks it unlikely that there are fifty times more speakers than organization members.
Finnish linguist Jouko Lindstedt, an expert on native-born Esperanto speakers, presented the following scheme to show the overall proportions of language capabilities within the Esperanto community:
In the absence of Dr. Culbert's detailed sampling data, or any other census data, it is impossible to state the number of speakers with certainty. Few observers, probably, would challenge the following statement from the website of the World Esperanto Association:
Ethnologue reports estimates that there are 200 to 2000 native Esperanto speakers (denaskuloj), who have learned the language from birth from their Esperanto-speaking parents. This usually happens when Esperanto is the chief or only common language in an international family, but sometimes in a family of devoted Esperantists.
The most famous native speaker of Esperanto is businessman George Soros. Also notable is young Holocaust victim Petr Ginz, whose drawing of the planet Earth as viewed from the moon was carried aboard the Space Shuttle Columbia in 2003 (STS-107).