便携笔记本
本章知识点
Economics is the study of how society manages its scarce resources. Scarcity（稀缺性）is the fundamental problem: society has limited resources and therefore cannot produce all the goods and services people wish to have. Economics studies how people make decisions, how they interact, and how the economy as a whole works.
The first four principles concern how people make decisions: People face trade-offs（权衡取舍）; the cost of something is what you give up to get it—opportunity cost（机会成本）; rational people think at the margin（边际）; and people respond to incentives（激励）。
The next three principles concern how people interact: Trade can make everyone better off; markets are usually a good way to organize economic activity (the invisible hand，看不见的手); and governments can sometimes improve market outcomes by correcting market failure.
还没有划重点：在左侧原文中选中一句话试试。