&gt;but in practice there&#x27;s a surprisingly large gap between that and a person who can speak fluently on complex subjects with no fear of being misunderstood, but makes occasional minor errors--or even usages which are grammatically correct, but sound stilted--that betray them as non-native.<p>Well the purpose of translation is communication, not hiding your nativeness, do I don&#x27;t see the point of this.<p>&gt;There&#x27;s a big jump between 99.9% and 100%<p>Well the jump is between 0.1%<p>&gt;and if you want a really professional translation job, you&#x27;re not going to settle for 99.9%.<p>That&#x27;s like saying if i wanted to hire an engineer to build me a nuclear reactor im gonna pass everybody who scored 99.9% on a test in favor of the magical unicorn who by virtue of being born in the beautiful blue glow of a reactor is the only being capable of scoring 100%.<p>Either the gap is actually bigger then 99.9-100 as you say, or the gap is so small as to be insignificant.<p>People can vary greatly in english skill if they are not native and while you can most likely figure out whether or not they were born where by their accents and their way of speaking, a sufficiently skilled speaker would give you no more trouble in communicating to you whatever complex ideas they might have in their mind.<p>The only reason I can think of of this restriction is protectionism, i.e. a translator union located in England would want to protect its members from competition and find it most convenient to claim a special status on nativeness without coming off as obviously anti-competitive.