Efficiency is a measure of the ability of your colonists to produce goods for the colony.
Productivity depends on two basic factors: Employment levels and happiness of the workers:
- Employment is simple: The closer to 100% employment you are, the more effective a given structure will be.
- Happiness is more nuanced: The more annoyed the workers, the lower their productivity. If their morale drops too low, they will instead protest and stop contributing to the output of a given structure.
Of course, the efficiency with which goods are produced at your colony can be further affected by a number of additional features: