FSI estimates are taken from diplomatics who study full time in preparation for their job. Not a good approximation for most people. This is a far better one:

FSI estimates are taken from diplomatics who study full time in preparation for their job. Not a good approximation for most people. This is a far better one: https://www.cambridge.org/elt/blog/wp-content/uploads/2018/10/How-long-does-it-take-to-learn-a-foreign-language.pdf https://www.cambridge.org/elt/blog/wp-content/uploads/2018/1...