sin

Often these languages are invented only for the amusement of the authors, but those who hope that their work may find general acceptance soon learn how difficult it is to attract even one other speaker for the new language.
It is interesting to observe that each new plan attracted those who had adopted Ido, and then moved from one novelty to another. Few language projects survived their inventors. Esperanto is now spoken by from one to three million people in 120 countries, Interlingua by perhaps a thousand in 25 countries and Ido by 200 in 10 countries.

'ESPERANTO-The New Latin for the Church and for Ecumenism' von Ulrich Matthias, S.21