It's a fair question. At least speaking from my experience, the figure varied depending on the type of work and the employment classification. I should also a

It's a fair question. At least speaking from my experience, the figure varied depending on the type of work and the employment classification. I should also add that 3-4 is number of full time employees, not contractors. For example, it wasn't unusual to see engineering managers with 20 direct reports as long as most were contractors. They usually had couple of full time employees who were senior or leads.