I've heard a few times in the media that there are more Klingon speakers than Esperanto speakers, but I can't believe this is true. So, how does the number of Esperanto speakers compare with say Klingon, Ido, Interlingua, Volapük, Toki Pona, Lojban, etc?
Let's get started with this site on Lojban:
The on-line Lojban mailing list, which constitutes the largest community of people using the language, has over 200 subscribers, with well over 20 regular posters as of this writing.
Experts on Quora agree that there might be around 30 fluent speakers of Klingon.
Volapük was really popular in its heyday, with up to a million "followers" (as we would probably say today) - that was back in 1889. Today, an article estimates the number of speakers to 20. Kind of sad when you think about it. Vola ne pük or something.
The wonderful, zen, minimalist Toki Pona is spoken fluently by at least a hundred people.
Phraseology in planned languages puts the amount of Ido speakers to 100-200 for Ido and a few hundred for Interlingua. For Esperanto it suggests 500'000 to 3.5 million speakers (with the sources quoted from 1989). The numbers are probably higher today, as we can see from the number of students in the Duolingo course.
Hands down, Esperanto is the most widely spoken of the ones you mentioned. Looking at the impressive amount of original literature in Esperanto (and a language needs both speakers and readers for literature to be produced), Esperanto definitely has more speakers - and not just a little bit more, but a whole lot more.
Volapük < Klingon < Lojban < Toki Pona < Ido < Interlingua < Esperanto
And to make it very clear:
Klingon < Esperanto
30 < 500'000 (at least)
We could even take the highest number, just for fun:
30 < 3'500'000
Let's see the numbers from the English Wikipedia. Important note: the definition of "speaker" is not precise. As most speakers of a planned language learned it as an L2, which level of knowledge and practice is enough to be considered a "speaker"? It is not as simple as counting the number of people in a country.
- Esperanto: L2 users: estimates range from 100,000 total (1999) to 10 millions total (1996) L1: Around 1,000 families involving around 2,000 children (2004)
- Interlingua: 1,500 (2000)
- Ido: 100-200 (2000)
- Interslavic: several hundreds (2012)
- Toki Pona: over 100 are said to be fluent (2007)
- Elefen: 800 on Facebook (2016)
- Klingon: Around a dozen fluent speakers (1996) (Planet Earth)
- Lojban: ??
Esperanto is the most spoken planned language, by at least 100-fold. You can also compare the numbers of the different languages on the Esperanto Wikipedia.
It's hard to get absolute numbers, but comparing relative numbers of speakers is possible. Numbers used in other answers are not comparable, because they come from different sources. So I decided to use one source: LinkedIn profiles. They have a fixed format for specyfing language proficiency with 5 levels: "elementary proficiency", "limited working proficiency", "professional working proficiency", "full professional proficiency" and "native or bilingual proficiency".
I took a list of some well-known conlangs and ran a lot of Google queries in the format: language name + proficiency level, e.g.
"esperanto * elementary proficiency",
"klingon * limited working proficiency",
"volapük * professional working proficiency", etc. I restricted each search to the LinkedIn domain with
site:linkedin.com and counted the results - each result meant one person who listed a particular language at a particular proficiency level. I had to go to the last page of the results, because the numbers reported by Google on the first page are widely inaccurate.
Here's what I got (note that Elvish is very often listed as a seprate language, even though it basically means either Quenya or Sindarin):
native full prof. prof. limited elementary Esperanto 59 118 148 252 483 Klingon 75 44 50 83 205 toki pona 3 6 10 11 29 Lojban 1 1 4 16 45 Elvish 12 5 5 16 26 Quenya 2 0 1 17 25 Sindarin 5 0 3 12 19 Na'vi 2 1 1 7 8 Volapük 2 1 1 4 6 Interlingua 0 3 1 4 1 Elefen 0 0 2 2 0 Ithkuil 0 0 0 2 2 Ido 0 0 1 1 0 Solresol 0 0 0 0 1
That's the raw data. Many different interpretations can be made, here's mine.
Probably the biggest surprise is the very high position of Klingon. Especially the "native" column makes me think that many Klingon entries are just jokes. There's simply no way there could be more native Klingon speakers than native Esperanto speakers. I would say that the whole group of artlangs (Klingon, Elvish, Quenya, Sindarin, Na'vi) is quite specific. These artlangs were never meant for actual communication between humans. Moreover, many people may learn them just because they are fans of Star Trek/Tolkien/etc and not because they are interested in langauges. Therefore, many speakers of artlangs may have a lower standard for what "proficiency" means.
Despite all this, we can't ignore the high position of Klingon. Wikipedia says it had "around a dozen fluent speakers" in 1996, and Yens Wahlgren's Bachelor's thesis says 20-30. These numbers seem underestimated. Klingon Language Wiki lists 38 "Klingonists of note", most of whom must have an advanced level in Klingon. It is made clear that it only lists people who have contributed in a special way to the community, so we can expect that the list of the speakers is longer, even in the Klingon Language Institute. Moreover, Star Trek is widely known and has fans around the globe - any dedicated fan with language learning aptitude may learn Klingon on his/her own without any association with KLI. Apart from that, among 604 respondents to the Klingon Questionnaire there were 93 who assessed their level as intermediate, 49 upper-intermediate and 16 advanced.
For comparing the number of speakers of the languages, I think it makes sense to sum for all the levels, except for "elementary proficiency". People may say they know a language at the elementary level if they just read a bit about it, and can't really use it. Therefore, I summed the number of people listing each language at the "elementary working proficiency" or higher. Here are the results:
Esperanto 577 Klingon 252 Elvish 38 toki pona 30 Lojban 22 Quenya 20 Sindarin 20 Na'vi 11 Volapük 8 Interlingua 8 Elefen 4 Ithkuil 2 Ido 2 Solresol 0
Esperanto has clearly the highest number of speakers, by any count. Some languages can grouped together, as the differences between them are not significant. As far as non-artlangs are concerned, toki pona and Lojban are clearly on the second place, with more speakers than the rest. The ordering is as follows:
- toki pona, Lojban
- Volapük, Interlingua, Elefen, Ithkuil, Ido, Solresol
If we compare Esperanto with artlangs, the ordering is:
- Elvish languages (Quenya & Sindarin), Na'vi
For the reasons I explained above, it's very hard to compare the number of speakers of artlangs to speakers of non-artlangs. My very rough guess is that the number of Klingon speakers has the same order of magnitude as the number of toki pona or Lojban speakers (that is, one or a few hundred). Elvish languages have fewer speakers, so the order of magnitude is probably similar as with the rest of the languages. It means that the order should be roughly like this:
- toki pona, Lojban, Klingon
- Volapük, Interlingua, Elefen, Ithkuil, Ido, Solresol, Quenya, Sindarin, Na'vi