Maximum productivity is achieved when a task is divided up into sub-tasks and individuals specialize in a sub-task.
Consider the task of making a pin. This task can be broken up into these 10 sub-tasks:
1. One person draws out the wire.
2. Another straightens it.
3. A third cuts it.
4. A fourth points it.
5. A fifth grinds it at the top for receiving the head.
6., 7., 8. Making the head requires two or three operations.
9. Putting on the head is a peculiar business.
10. To whiten the pins is another.
A person performing all these sub-tasks could make perhaps 20 pins in a day. Thus 10 persons produce 200 pins in a day.
When each person performs only one sub-task, the 10 persons working together can collectively produce 48,000 pins in a day. By dividing up the labor there is a 250-fold increase in productivity.
— Extracted from Wealth of Nations by Adam Smith