A common argument made by proponents of international auxiliary languages - a.k.a. "auxlangers" - is that the European Union needs a single working language and the present situation is way too expensive. Therefore the EU should adopt an auxlang, be it Esperanto or Interlingua, as its sole official language. But are these people right?
What does the EU actually spends on translation?
Let's consider a few figures. According the Publication Office of the European Union - the body that is responsible for the publication of EU documents - including their translations - the EU spent about 343 million Euro on translation in 2020. Also the EU has about 447 million residents. So a quick calculation tells us that the EU spends about 0.76 Euro per EU resident a year on translation. That is not really that much money, is it?
What are the opportunity costs for the average EU citizens of learning Esperanto or Interlingua?
According to the advocates of Esperanto, learning the language developed by Zamenhof takes about 150 hours to learn Esperanto. Eurostat states that the average hourly wage in the EU is about 28.50 Euro. (A quick note: this figure is inflated by a small portion of high income earners and the majority of EU residents will make less than this amount, but I could not find an estimate of the median hourly wage in the EU).
So the opportunity cost of learning Esperanto is 150 x 28.50 = 4,275 Euro - I do not think Interlingua will gives us a different figure. In order to recoup this cost, one needs to live for about 5,625 years. Or put simply: learning Esperanto or Interlingua just to save money for the average EU citizen (not the poorest people in the world) would be a bad investment.
Will the adoption of Esperanto or Interlingua actually eliminate translation costs?
No. Even if the EU will not translate anything anymore, the individual members states will still have to translate EU documents for its citizens. So the cost of translation are simply shifted from the EU to the member states. And as we have seen above, the actual per capita costs of translation for the EU are virtually negligible. A shift to a single working language will simply be not worth the investment.
Would the average EU-citizen even bother to learn Esperanto or Interlingua?
Most EU documents are technical in nature (e.g. product standards, various regulations) that are hardly comprehensible to the average EU-citizen, even in their native language. Those documents which comprise virtually all of EU texts, are simple not intended for casual readers but for manufacturers, law enforcement and lawyers.
Since the average EU-citizen hardly deals with EU documents on a regular base, there will be virtually zero incentive to learn whatever language these are written in. To quote Mark Rosenfelder:
“Languages take immense effort to learn, and people will only learn them if it's socially or economically inescapable.” (When do people learn languages?)
So even if the EU would decide to make Esperanto or Interlingua its official or sole working language, most EU-citizens won’t be directly affected by it.
Is implementing Esperanto or Interlingua as a working language even feasible?
Short answer: no. The EU employs about 43 thousand staff members. Contrary to the public image of rank and file bureaucrats, these civil servants are actually busy preparing a wide range of proposals on policies, standards and so on. Given the nature of diplomacy, complex negotiations require a lot of work.
When are these people going to learn a new language, while there are more pressing matters like climate change, energy security, Russia and so on? How long will it take until every EU employee speaks Esperanto or Interlingua at such a level they will be able to pursue complex negotiations? Remember such work is hard, even in your own native tong.
Would adopting a single official language of the EU not be a powerful symbolic signal?
Yes, it would and is also why auxlangers - Esperantists in particular - are so eager to push for such a move. However, it would also fuel euro-skepticism across the EU and hence potentially risking the breakup of the European Union. Imagine how easily populist politicians around Europe could claim that the "EU is going to impose a fake language upon us in order to destroy our culture" or something like that. Regardless whether such claims would be true or not - lies did not prevent Brexit after all.
Given that the adoption of a single official language offers little to no economic benefits, why would the EU even consider such a controversial move? The so-called language question only exists in the minds of auxlangers and has already been effectively solved. Both the EU and its member states have far more important issues to deal with.