Of course a 50-hour employee is productive, but would you say consistently over a longer number of weeks he's 12.5% more productive than a 40-hour employee?
To give myself as an example: I work out 3-4 times a week, spend my time effectively reading books, playing the piano regularly and spend some quality time with my wife. These activities I would not be able to do would I work consistently 60+ hours a week. Nonetheless, it has had and continues to have a profound positive impact on my energy levels, motivation, communication and creative reasoning.
To give myself as an example: I work out 3-4 times a week, spend my time effectively reading books, playing the piano regularly and spend some quality time with my wife. These activities I would not be able to do would I work consistently 60+ hours a week. Nonetheless, it has had and continues to have a profound positive impact on my energy levels, motivation, communication and creative reasoning.