In the 70’s thru early 90’s, I used to hear people saying
we should all be studying a language called Esperanto, because ‘Esperanto is the world’s most widely spoken constructed, auditory language.”
This was also the era when we were told that America had to finally learn how to use Metric measurements “Like the rest of the civilized world”.
Neither trend, Esperanto or Metric Measurements in everyday usage ever quite caught on in the States.
Yes and in the mid 1980s the yen was a very strong currency and all of the experts, pundits, etc. said we would all be speaking Japanese by 2010.
There are more people speaking Klingon than Esperanto these days.