財政政策與景氣波動：不完全競爭總體模型之分析

Abstract

總體經濟模型結合了不完全競爭的市場特性，為市場造成了扭曲。80 年中期以後，「不完全競爭的總體經濟理論」發展至今多如恆河沙數，本篇論文試圖將產業經濟的特質與市場的調整機制納入模型設定中，從新檢視不完全競爭的市場特性將如何影響景氣波動與最適財政政策，希冀對不完全競爭的總體經濟模型，有更深刻的了解與認識。 在第一篇文章，我們將不完全競爭的市場結構與傳統實質景氣循環模型結合，並向兩個方向延伸：第一，我們結合產業經濟的觀點，考慮專業化分工是否具有規模報酬的特性；第二，我們考慮進入成本的擁擠效果–在產業經濟研究中，市場中既有的廠商家數越多，廠商的進入成本將越高，例如廣告成本。將這兩種效果引入模型，我們發現，專業化分工的程度與進入成本的擁擠效果將左右經濟體系複均衡的存在性。另外，專業化分工的效果支配著消費性政府支出對私人消費與實質工資的影響。最後，考慮進入成本的擁擠效果，我們發現隨著政府支出增加，個別廠商的生產將會提高，而並非一個常數。 在第二篇文章，我們假設個別廠商的生產技術具有規模報酬遞增的特性。另外，依循公共財政學的觀點，我們將政府支出的生產性功能納入模型，同時也考慮政府的生產性支出所衍生的擁擠效果。最後，為了充分了解獨占力指數與專業化分工程度對經濟體系的影響效果，我們將獨占力指數與專業化分工程度用兩個參數分別代表。在這個架構下，我們發現幾個結論。第一，經濟體系複均衡的存在性與專業化分工程度有關但與獨占力指數無關。第二，在具有比例式相對擁擠效果下，政府的生產性支出彈性將無法左右經濟體系複均衡的存在。第三，個別廠商規模報酬遞增的程度越大，則經濟體系越難出現複均衡現象。第四，我們以實質景氣循環模型所採用的參數值進行分析，結果發現，在單純具有比例式絕對擁擠效果情況下，資本產出彈性趨近於零，勞動產出彈性趨近於一，而這結果與實證資料相吻合。 在第三篇文章，我們分析當市場同時存在消費外部性與生產外部性的情況下，政府如何制定最適的財政政策。另外，我們亦考量生產專業化具有規模報酬遞增的特性與個別廠商的生產技術具有規模報酬遞增的特性。藉由市場調整機制的不同，我們發現幾個結論。第一，若政府同時具有消費稅與所得稅兩項政策工具，則消費稅是用來矯正消費外部性最適的政策工具，而所得稅是用來矯正生產外部性最適的政策工具。第二，最適所得稅的制定將會因市場調整機制的不同而有所改變。第三，當市場中的廠商家數固定不變，則最適的政府支出佔所得的比例將等於政府支出的生產彈性，相反的，當市場中的廠商家數可以自由調整，則最適的政府支出佔所得的比例將不等於政府支出的生產彈性。第四，當生產專業化具有規模報酬遞增而且報酬遞增的程度夠大，則市場自由進出之下所決定的廠商家數有可能低於社會最適的廠商家數。

When imperfect competition is introduced to a general equilibrium macroeconomic model, the market allocation mechanism ceases to be efficient. Since the mid-1980s, there have been a vast number of articles that have been discussed in the context of imperfectly competitive macroeconomic models. This thesis attempts to introduce the features of both industry organization and adjustment mechanisms to our analysis, and in so doing reviews how the business fluctuations and government policies are affected by the imperfectly competitive market structure. It is hoped that we can arrive at a better understanding of imperfectly competitive macroeconomic equilibrium models. In the first essay, we introduce two features to our analysis. First, in line with the viewpoint of industry organization, we consider the feature of returns to production specialization. Second, we consider the congestion effect of the start-up cost. In the industry organization, the greater the number of firms, the greater is the cost of product differentiation. This implies that the cost of initial advertising to make consumers aware of a new brand is greater. By introducing these effects into our model, several main findings emerge from the analysis. First, we find that the necessary and sufficient condition for equilibrium indeterminacy is closely related to the extent of production specialization and the congestion effect of the start-up cost. Second, the effects of government spending on consumption and real wages depend on the extent of production specialization. Third, the output level of an individual firm is positively related to fiscal expansions, provided that the congestion effect of the start-up cost exists. In the second essay, we suppose that the production technology for individual firms exhibits the feature of internal increasing returns to scale in imperfectly competitive industries. In line with the literature in the public finance field, we consider the role of productive government spending that is subject to the congestion effect. In addition, in order to clarify whether the crucial factor for the local indeterminacy is production specialization or monopoly power, we specify two distinct parameters to reflect the returns to production specialization and the degree of monopolistic competition. Equipped with these features, several interesting results are derived from our analysis. First, the necessary condition for equilibrium indeterminacy is independent of the monopoly power. Second, in the presence of proportional relative congestion, the equilibrium indeterminacy disappears even if productive government expenditures are incorporated. Third, when the production technology of a private firm possesses the feature of internal increasing returns, the possibility of the emergence of local indeterminacy is negatively related to the extent of the internal increasing returns to scale. Fourth, we adopt the parameters set in the existing RBC works, finding that under the situation where public services are subject to purely proportional absolute congestion, the output elasticity of capital is close to zero and the output elasticity of labor is close to one. This result is consistent with the empirical findings. In the third essay, we analyze the optimal fiscal policies in the presence of consumption and production externalities and consider both the role of the extent of increasing returns to specialization and the role of internal increasing returns to scale. By introducing three differential types of adjustment mechanisms, several main findings emerge. First, if both consumption and income taxes are available to the government, the consumption tax should be utilized to correct consumption externalities and the income tax should be utilized to remedy production externalities. Second, the inclusion of three different types of adjustment mechanism plays an important role in governing the implementation of optimal income taxes. Third, the optimal ratio of government expenditure is solely determined by the extent of production externalities if the number of firms is constant, while the result should be modified if the free entry and exit of firms is brought into the picture. Fourth, free entry in the competitive equilibrium may result in under entry, provided that the degree of increasing returns to specialization is sufficiently strong.