经济增长与危机(第7章)

曼昆始终喜欢从supply/demand的角度分析宏观经济问题，很有意思。。

1. Supply:  economic output，和capital stock成正比。
经济学家对output per worker也很有兴趣，并在此基础上引伸出Marginal product of capital(MPK)。MPK的含义是每多一个工人，平均每个人能多产出多少(平均产出是output/labor-count). "How much extra output a worker produces when given an extra unit of capital."

2. Demand: demand comes from consumption (c) and investment (i).  Saving rate determines the relation between c and i:
output = c+i
c = output(1-s) + i