需求曲线的平移和转动

我朋友的解释是：

从价税：系依价格的高低课征租税，今以r代表从价税税率，则从价税之净需求曲线应为(1－r)P(q)，故税后的市场均衡应为(1－r)P(q)＝S(q)；

从量税：系指租税依数量来课征，今以ｔ表示从量税之单位税收，则税后之市场均衡为：P(q)＝S(q)＋t

这进一步解释了平狄克的英文答案：

Consider the effect of imposing a 20 percent sales tax on automobiles in the short and long run. To analyze the influence of the tax, we can shift the demand curves because consumers are forced to pay a higher price. Notice that this tax is an ad valorem tax. The demand curve does not shift parallel to the old ones, but pivots to reflect the higher tax paid per unit at higher prices.

Unlike the automobile market, the gasoline demand curve is not characterized by a stock adjustment effect. The long-run demand curve will be more elastic than the short-run one, because in the long run substitutes (e.g., gasohol or propane) will become available for gasoline. We may analyze the effect of the tax on gasoline in the same manner as the tax on automobiles. However, the gasoline tax is a per unit or specific tax, so the demand curves exhibit a parallel shift.

楼主也看PINDYCK的书啊~我才开始看~以后请教啊

干脆成立一个平狄克－中微－学习小组算了。呵呵。越学越爱的一本标准中微教材。

鄙人认为，只要吃透一本微观书，勤思考，就所向披靡了。

hao

都是学中级经济学的啊？我还在学初级的，看来进错地方了！

我还是再看看书再来把…………

个人认为可以从税收的对于需求影响的传导机制上理解。对于从价税而言，其实际上通过提高商品价格使消费者的实际收入相对减少，从而降低消费者在相应商品上的消费数量。但是，从量税是以实际获得商品数量征税，即是说消费者的花费是以消费商品的数量的多少而发生相应的变化而并非商品的价格。在反需求曲线上，从价税改变的是数轴的相应数值，而从量税使曲线更加平坦，从而使商品变的更加富有弹性，使消费者在税收的分担比例上得到较低。