Translate the following English sentence to French:
"There is no statistical data on this very specific subject, because we have to work with figures that are very difficult to obtain, given that we are talking about illegal immigration on the one hand and about illegal employment on the other, but it seems to us at first sight that this number is rather high."
Il n'existe aucune donnée statistique aussi précise sur la question, nous sommes contraints de travailler sur la base de chiffres très difficiles à obtenir, étant donné qu'ils concernent des problèmes d'immigration illégale, d'une part, et de travail illégal, d'autre part.