This is known as the "pareto principle" but it was observed long before then. In terms of scientific sources, what sources do you have that everyone makes the s

This is known as the "pareto principle" but it was observed long before then. In terms of scientific sources, what sources do you have that everyone makes the same contribution? Of course 80/20 is a rule of thumb, but a small group of people do the bulk of the work in most organizations.