政府不干預，市場就一定自由嗎？
我們要先弄清楚perfect competitive market和free market的區別。這兩者其實經常被人認爲是同一種東西，然而并不是這樣。
perfect competition根據wiki:
Such markets are allocatively efficient, as output will always occur where marginal cost is equal to average revenue i.e. price (MC = AR).
in the long-run, productive efficiency occurs as new firms enter the industry; At this point, price equals both the marginal cost and the average total cost for each good (P = MC = AC)
很多人認爲的政府稅收導致dead weight loss 從而導致total surplus減少其實模型都是依據perfect competitive market來看的。至於free market我認爲則是一個ideological term，對於經濟學討論沒有用。我們其實指的都是perfect competitive market。
那麽政府其實可以損害perfect competitive market，但是并不是只有政府可以損害。Monoply甚至Monopsony都可以損害。
