具外顯效果下從價與從量稅制福利效果之比較—有限理性的觀點

Abstract

傳統探討從價與從量兩種稅制福利效果之比較的文獻都是建立在人們是完全理 性的基本假設上。然而，近年來隨著行為經濟學的興起，愈來愈多的證據顯示， 人們對租稅的反應並非如同傳統所假設地那麼完美。如同 Chetty et al. (2009) 所 述，實證的資料顯示，人們在購買商品時，常會低估課稅對需求的影響，文中將 此稱之為「外顯效果」(salience effect)，並探討當租稅的課徵具有該效果時，課 稅的效率成本以及租稅歸屬的問題。實際上，西元 1848年 John S. Mill 便以理 論模型探討稅率缺乏能見度所造成的財政幻覺 (fiscal illusion ) 會如何影響到投 票行為以及政府的規模之課題。有鑑於此，本計畫擬從「有限理性」的觀點出發， 重新探討當租稅的課徵具有外顯效果時，從價與從量此二種稅制的福利效果之比 較。承如 Chetty et al. (2009) 乙文所述，因為從價稅制相較從量稅制的能見度為 低，本計畫初步發現：給定該二種稅制的單位稅負相同且廠商的供給線為水平的 情況，由於從價稅制的能見度較低，租稅負擔在從價稅制下受到低估的程度較嚴 重。市場均衡時，課徵從價稅制的消費量與稅收會高於課徵從量稅制，消費者支 付的代價則會相等，且低估稅負的突出效果可以緩和租稅造成的超額負擔，因而 由社會福利的觀點來看，從價稅制會高於從量稅制。此結果與異於傳統認為完全 競爭市場下課徵從價稅與從量稅的福利效果相同之認知。至於不完全競爭的市場 結構則有待日後計畫的執行再進行討論。

A central assumption in public economics is that agents’ reactions to tax policies are fully rational. Specifically, canonical results on the comparison between ad valorem and specific taxation all rely on this assumption. However, more and more evidences suggest that individuals’ reaction to many types of tax and transfer policies are not correspondent to the traditional optimization problems. For example, Chetty et al. (2009, AER) analyze the effect of “salience” on behavioral responses to commodity taxation. They find that commodity taxes that explicitly labeled with prices to consumers when shopping (and are thus more salient) have much larger effects on their demanding. They also pointed out: the degree of inattention to ad valorem taxation is smaller than that to specific taxation (see footnote 26). By the reason, this project intends to compare specific and ad valorem taxation on commodities in a bounded rationality model of tax salience. It firstly finds that: in the competitive markets, as long as per unit taxes are equal and the individual supply curve is flat, both the equilibrium output and tax revenue are higher under the ad valorem scheme than under the specific scheme, whereas the equilibrium prices are equal since the ad valorem scheme is more salient than the specific scheme. The imperfect competition model will be discussed in future analysis of this project.