Give a stream of consciousness and then the final answer. "Nobody Knows You When You're Down and Out" is a blues standard written by Jimmy Cox in 1923. Its lyric, told from the point of view of a one-time millionaire during the Prohibition era, reflects on the fleeting nature of material wealth and the friendships that come and go with it. As a vaudeville-style blues, it was popularized by Bessie Smith, the preeminent female blues singer of the 1920s and 1930s. Since her 1929 recording, it has been interpreted by numerous musicians in a variety of styles.

Answer this question: who wrote nobody knows you when you're down and out?
The important part for answering this question is: "Nobody Knows You When You're Down and Out" is a blues standard written by Jimmy Cox in 1923.
So, the final answer is Jimmy Cox.