为什么会有货币？
Why does money exist?
货币作为通用媒介，降低以物易物的成本。
Money is a common medium that cuts barter cost.
来源 · Source
N. Gregory Mankiw,《Principles of Economics》第8版,Cengage,2017;中译《经济学原理》北京大学出版社
N. G. Mankiw, Principles of Economics, 8th ed., Cengage, 2017; Chinese ed. Peking University Press
独立核验依据 · Independent verification: 核验依据 2 cengage.com