If it takes three workers 10 hours to dig a hole, how many hours would it take six workers to dig the same amount? Simple, right? Half the time. But try using that logic where complex projects are involved and you’ll soon become unstuck.

It may feel counterintuitive, but adding manpower to a late software project makes it later. This simple guiding principle – known as “Brooks’ Law” – was written by software engineer, Frederick P. Brooks, in his 1975 essay “Mythical Man Month”. Brooks explains that men and months are interchangeable commodities, only when a task can be partitioned among many workers with no communication among them.

Consider making a toast at a dinner party. If there are only a few people it takes a matter of moments to clink glasses with each of them. Expand the guest list and suddenly there are many people in the room that you don’t “cheers” with, or if you do, it takes a great deal more time and effort.

Human beings work in different ways, in different environments, and at different rates – how many hours they’re on the clock is not indicative of the speed, volume and quality of their output.