This is the simplest yardstick of economic performance. If one person, firm or country can produce more of something with the same amount of effort and resources, they have an absolute advantage over other producers. Being the best at something does not mean that doing that thing is the best way to use your scarce economic resources. The question of what to specialise in–and how to maximise the benefits from international trade–is best decided according to comparative advantage. Both absolute and comparative advantage may change significantly over time.