HOW MANY PEOPLE SPEAK ESPERANTO ? OR : ESPERANTO ON THE WEB

We suggest an updated estimate of the number of Esperanto speakers worldwide, based on the number of people in Facebook who indicate that they speak the language. A simple calculation accompanied by reasonable refinements leads to a number of approximately two million Esperanto users within the internet community alone, probably significantly more worldwide.


INTRODUCTION
The internet revolution has had a huge impact on Esperanto, the international language created in 1887 by Dr. L.L. Zamenhof.A single event that perhaps best represents this revolution is the addition (in April 2012) of Esperanto to the exclusive club of languages in Google Translate.Other significant events are long-term processes such as the dramatic growth of the Esperanto community in social networks and the ongoing development of the Esperanto Wikipedia.In this article we present, perhaps for the first time, a scientifically controllable method to assess the number of Esperanto-speakers worldwide.Our method uses the number of Esperanto-speaking users of the social networks, in particular Facebook.We state the major assumptions and limitations of this method, compare the figures to those of registered users of web-based Esperanto courses, and finally check its validity by using it to estimate the numbers of speakers of several other languages, which, unlike Esperanto, do have an established census.

ANALYSIS AND RESULTS
Over the years, estimates of the number of Esperanto speakers have varied greatly, from a modest 100 000 up to 16 million.These estimates were based on membership statistics and on sales data of Esperanto textbooks [1].The only way to determine accurately the number of people who speak Esperanto would be to conduct a world-wide census, which has never been done.The most comprehensive survey was performed by Sidney S. Culbert of the University of Washington, Seattle, USA.He conducted interviews in dozens of countries around the world and tested for "professional proficiency".Based on this survey, he estimated that Esperanto has about two million speakers worldwide.
In recent years, the Esperanto web-community has been growing rapidly.The internet has also provided us with more accurate tools to estimate the size of the Esperanto community.In lectures on Esperanto [2][3][4] we list several parameters to assess the strength of Esperanto in the Web: the number of hits on "Esperanto" in search engines such as Google, the appearance of Esperanto in social networks and learning platforms, and the growth of the Esperanto Wikipedia.The number of hits of the word "Esperanto" on Google often surprises unprepared listeners.The number of hits in 2014 approached 50 million, and it has been even higher (above 80 million hits) earlier (these changes probably depend on how Google counts hits).
In 2013 we published [5] a new method to estimate the number of Esperanto speakers in the world, based on social network statistics.The number of Facebook users indicating that they speak Esperanto is 320,000 (at the end of 2014).The current figure can be checked at the Facebook's Esperanto site [6].This number is of the order of the number of users in Lernu.net[7], the most popular online learning platform for Esperanto: in 2013 Lernu.net reported 150 000 registered users [8] and between 150 000 and 200 000 monthly visitors.
In 2011 Facebook stated it had approximately 750 million registered users [9].The current figure probably approaches one billion, but this number is likely to overestimate the number of real users, because it includes inactive accounts or deceased people.Thus a reasonable estimate might be that about 10 % of the world population uses Facebook.Combining this figure with the number of "Esperanto speakers" on Facebook, one could by simple extrapolation estimate that the number of Esperanto speakers throughout the world is 1-2 million (if 10 % of the world population uses Facebook, one has to multiply the Facebook number (e.g.300 000) ten times to find the number of Esperanto speakers worldwide).
Of course, for a serious analysis one must consider additional factors, such as the fact that the number of people claiming to know Esperanto is probably higher than that of those who speak it well (similarly only a fraction of the people registered in a language course end up as speakers of the language).However, this has also been the case in the past, when calculations of Esperanto speakers based on membership in Esperanto organizations did not take into account the fact that many members of such organizations might not speak Esperanto, even though, for various reasons, they had joined those organizations.
On the other hand, a large part (probably most) of Facebook users who do speak Esperanto do not indicate this in their accounts; so the true number of Esperanto speakers on Facebook may be bigger than the official one.A third refinement that must be taken into account is that the Facebook proportion may presumably be safely extrapolated only to that part of the world population which uses the Internet.The percentage of Esperanto-speakers in the population who do not use the Internet may be lower, since such people would have less resources to learn and use Esperanto, such as online courses and Esperanto websites.The percentage of the world population which uses the Internet was approximately 40 % by the end of 2013 [10], that is 2,8 billion people.
Let us assume that only half of the Facebook claims of competence in Esperanto are reliable, but on the other hand only a third of the Esperanto speakers who are using Facebook are aware of the option to indicate in their Facebook profile that they know Esperanto and have actually done so.With these numbers it is straightforward to calculate 1 that the number of people who speak Esperanto among those who use the Internet is approximately 2 million [11], and in the whole world's population it is probably significantly larger.
The most serious criticism of such an estimate is, as mentioned above, that supposedly not all people who indicate that they speak Esperanto are really Esperanto speakers -though they probably do have some knowledge of Esperanto.One way to assess the credibility of the number of Facebook users who claim to speak Esperanto is to test similar data for other languages; in other words, to attempt this method in order to find out how many people speak other languages than Esperanto, which do have established statistics.If the results obtained for those languages make sense, then the result for Esperanto is probably valid as well.For example, for French the Facebook number is 42 million out of an estimated number of 190 million speakers worldwide, while for German it is 23 million out of some 200 million.As a representative of small languages we may consider Hebrew; here the Facebook number is 1,3 million, about 15 % of the number of estimated speakers in the world (9 million).From these data it seems that the number of speakers of any language on Facebook is about 10-20 % of the actual worldwide number of speakers.Hence 300 000 Esperanto speakers in Facebook out of 2-3 million Esperanto speakers worldwide is consistent with the percentage appropriate for other languages.
However, taking a very different case -the fictitious Klingon language (a constructed language spoken by the fictional Klingons in the Star Trek universe) gives a number of 250 000 Facebook users who claim they speak it.This figure could probably be associated with the numbers of Star-Trek fans rather than with speakers of the Klingon language.
Finally, these data should be taken with a grain of salt, given the Facebook disclaimer on all language-pages: "This Page is automatically generated based on what Facebook users are interested in, and not affiliated with or endorsed by anyone associated with the topic."

SUMMARY
In summary, the Esperanto web community is probably much larger than some conservative estimates of Esperanto speakers, based on membership statistics, and agree with the most comprehensive survey attempted by "traditional" methods.The internet, and particularly