Imagine a translator who is 50% fluent in source language and 100% fluent (native) in target language. He would often misunderstand the source text and, even though he can produce target language natively, the translation would be incorrect.<p>Now imagine a translator who is 100% fluent in source language and 50% fluent in target language. He completely understands the source text and, using only simple sentences, can accurately convey the meaning in the target language.<p>This thought experiment demonstrates that the knowledge of source language is <i>far</i> more important for the accuracy of translation.