“…to his satisfaction he realized that he had proved conclusively that if life is going to exist in a Universe of this size, then the one thing it cannot afford to have is a sense of proportion.”
-Douglas Adams, HHGTTG-2
The Frisch-Waugh-Lovel theorem is a well-known result in theoretical economics. The theorem goes back to the 1933 paper of Frisch and Waugh. In this paper, they consider regressing an outcome variable...