Comparative Advantage

In 1817 David Ricardo invented comparative advantage which says that a poor country, which may be worse at producing every possible good than the rich country, can still make gains from trade. This is counter-intuitive because competitive advantage would suggest that if your friend, Lee Hsien Loong, is better than you at both mathematics and politics it would be best not to compete against him in either because you'll lose. What comparative advantage says is that even if a country is better than you in many things, how much better they are will vary, and they should focus on what they are relatively best at, and you in turn as the developing country should focus on what you are relatively least bad and and trade. So in the previous example, Lee Hsien Loong should go into politics and full-time and you mathematics and then trade.