Word Error Rates (WER), are the standardised metric for understanding that. The number is the number of words you would need to add, remove or replace per 100 w

Word Error Rates (WER), are the standardised metric for understanding that. The number is the number of words you would need to add, remove or replace per 100 words (so lower is better). Spanish these days is often down in the 2-3 region, English in the 4 region, and Finnish in the 7-8 region. Slovenian is typically 15-20, and Punjabi, Bengali and other SE Asian languages hit at 40+. By far the biggest factor seems to be the amount of translated material in that language, followed by how "obvious" the rules of the language are making it easy to decompose algorithmically.