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.
Adaptive expectations
A theory of how people form their views about the future that assumes they do so using past trends and the errors in their own earlier predictions. Contrast with rational expectations.
Adverse selection
When you do business with people you would be better off avoiding. This is one of two main sorts of market failure often associated with insurance.
