[考題] 105關務財政學-外部性
出處:105年關務三等財政學第1題
已知鋼鐵的供給與需求函數分別為 Q = 10P,Q = 3,500-10P,其中Q為鋼鐵的數量。
鋼鐵的生產會引起邊際外部成本為MEC = 0.05Q。試求鋼鐵的市場均衡數量為何?
達到效率的鋼鐵數量為何?政府每單位課徵多少的皮古稅以達到效率水準?
皮古稅的課徵使社會福利增加多少?
我有疑問的是最後一小題社會福利的部分,上面三小題簡單提供答案以供參考:
1.市場均衡數量 = 1,750,價格為175
2.達到效率的數量 = 1,400,價格為250
3.政府每單位課徵70元皮古稅
4.課稅後社會福利增加多少?
附上簡圖:http://imgur.com/oOqYGsj
個人認為是要算無謂損失的面積(也就是圖中斜線面積)
算法為(262.5-175)*350*1/2
算出來答案為15,312.5
但網路上找到兩份擬答答案皆為12,250
他們的算法是(1750-1400)*70*1/2
想請教各位的想法,還請各位多多指教,非常謝謝!
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