Efficiency 經濟效率 MC

[學生提問]

問：點解A錯? (Efficiency 經濟效率)

DSE 13/1/20
A beekeeper keeps the bees for their honey. The bee-keeping benefits the farmers in the orchard nearby because the bees help pollinate the fruits in the orchard. Which of the following statements about this case is correct?
A. There will be a divergence between private and social benefits and the honey is over-produced.
B. The beekeeper should be subsidized by the government to improve economic efficiency.
C. If the value of honey is higher than the value of fruits, there is no need for the government to intervene to correct the externality.
D. There will be no divergence between private and social benefits if the orchard nearby is owned by the beekeeper.

相信大家都應該知道上述題目答案是D，基於果園是養蜂人所擁有，傳播花粉的好處不是「external界外」，而是「internal 界內」。故此，沒有所謂的external benefit界外得益。

我的私補學生都應該很清楚，我在課堂上經常提及，面對任何Efficiency 經濟效率，必先界定其情況，而定義上有2個講法：
1. Underproduction 生產不足 / Overproduction 生產過剩
2. MB > MC / MC > MB

選項A錯的原因，是前言不對後語。在有external benefit界外得益下，SMB > SMC 社會邊際得益大於社會邊際成本，多生產一點對社會還有得益，故此Q產出少於Efficient Output 經濟效率數量(Q*)，應該是Underproduction 生產不足。

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