Inventions are one of the chief examples of "positive externalities" (an economist's name for a beneficial side-effect that falls on those outside a transaction or activity). One of the central concepts of economics is that externalities should be internalized: unless some of the benefits of this positive externality can be captured by the parties, the parties will be under-rewarded for their inventions, and systematic under-rewarding will lead to under investment in activities that lead to inventions. One important economic effect of the patent system is to capture those positive externalities for the inventor (or the party that hired the inventor), so that the economy as a whole will invest a more-closely-optimum amount of resources in the process of invention.