本文嘗試利用兩國動態一般模型 (dynamic stochastic general equilibrium, DSGE)架構，分析資本市場存在的不對稱摩擦現象，藉由設定不同兩國債券調整成本的三種形式，模擬兩國總體變數在本國生產力衝擊下的影響分析。本文模型架構主要遵循Bergin et al. (2007)，文中廠商的商品訂價方式採生產者貨幣訂價 (producer currency pricing, PCP)，即廠商的訂價行為依照本國貨幣作為計價單位，透過名目匯率轉換為外國消費者面對的商品價格，單一價格法則 (the law of one price, LOP)在此訂價方式下成立；本文模型的商品訂價方式改採當地貨幣訂價 (local currency pricing, LCP)，本國廠商以當地貨幣作為計價單位訂定其商品價格，該訂價方式廣為近來文獻所採用，並符合已開發國家之訂價行為，故採用此訂價方式。 電腦模擬本文資本市場的三種不同設定，在本國生產力具有 的外生衝擊下，資本邊際生產力的提高致使本國廠商增加投資，代表性個人資金借貸的管道可透過本國債券與外國債券進行融通，而本國代表性個人在買賣本國債券時無需負擔債券調整成本，在購買外國債券時則需負擔債券調整成本，此一設定即在反映資金借貸的摩擦情形；變數的動態模擬結果顯示，資本市場的不對稱摩擦，將透過兩國間的經常帳變化條件，影響資金借貸的流通，對於兩國總體經濟變數具有顯著影響。

本文以Paolo Gelain(2010)所建構的SWBGG模型，結合Smets & Wouters(2003,2005,2007)及Bernanke,Gertler and Gilchrist(1999)，建構具有金融摩擦(financial frictions)的動態隨機一般均衡模型，用台灣的總體時間序列1980Q3-2011Q4的季資料，拱用七種觀察值：分別為實質GDP成長率、實質投資成長率、實質消費成長率、實質工資成長率、GDP平減指數成長率、工時和金融業隔夜拆款利率利用貝氏估計做參數估計，主要分析分析不同衝擊下對於台灣景氣循環波動影響，及外部融資溢酬與景氣波動的相關性。

在次級房貸風暴之後，各國赤字大幅增加。如希臘與愛爾蘭，其主權債務違約風險皆大幅升高。面對這樣的困境，政府該如何實施財政政策，以防止主權債務危機的發生?本篇文章在DSGE模型之下，以Uribe(2006)的設定為基礎架構，額外增加了產出方程式以使國家產出能由模型內生決定。並加入了政府支出與產出之間的關係式，以討論在面對正的景氣衝擊與負的景氣衝擊時，政府使用正向景氣循環政策和負向景氣循環政策對於政府倒債率的影響。最後發現當政府使用負向景氣循環政策和較弱的順向景氣循環政策時，政府的倒債率會和技術衝擊有反向的關係。而當政府使用較強的順向景氣循環政策時，政府的倒債率會和技術衝擊有正向的關係。從此結果，我們推論在後金融海嘯時期，希臘與愛爾蘭等國家，應使用較強的順景氣循環政策以降低其主權債務危機的發生機率。 / After the subprime crisis, many government deficits rose sharply, especially Greece and Ireland. Their default rate rose greatly than before. Under this difficult situation, what kind of fiscal policy should the government enforces to prevent it from bankruptcy? We follow the model in Uribe (2006) as our framework but adding the production function and the government expenditure function to analyze the effects of different fiscal policies on the government default rate. The results tell us that when the government uses countercyclical fiscal policy and weak procyclical fiscal policy, the change of the default rate is opposite to the technical shock. On the contrary, when the government uses strong procyclical fiscal policy, the default rate is positive relation with the technical shock. This implies that governments, such as Greece and Ireland, should use strong procyclical fiscal policy to reduce their sovereign risk under the recession.

美元在世界上具有獨特的地位，大部份在國際上貿易的商品都以美元做為訂價，Devereux, Shi and Xu (2007)依此情況而把美元稱為國際上的參考貨幣(reference currency)。本文即以美元為參考貨幣的情況，建立一兩國動態隨機一般均衡(Dynamic Stochastic General Equilibrium)模型來探討在世界經濟體系中，有參考貨幣時，貨幣衝擊對兩國經濟體系的影響，以及當面對外在環境衝擊時，兩國政府應該如何選擇適當的貨幣政策。結果發現，擁有參考貨幣的國家發生貨幣衝擊時，對兩國的產出都有正面的影響，然而非參考貨幣國家發生貨幣衝擊時，反而有以鄰為壑(beggar-thy-neighbor)的效果。而在面臨外在環境衝擊時，選擇穩定通貨膨脹的利率法則對兩國而言都會帶來較好的福利效果。 / The U.S. dollars in the world possess a unique position; the majority of the international tradable goods are priced in the U.S. dollars. This paper sets up a two-country DSGE model where the U.S. dollar serves as the reference currency to quantitatively examine the impacts caused by the monetary shocks, as well as how both governments should adopt their monetary policies when facing external shocks. The results show that there are positive impacts on both countries' outputs when a monetary shock occurs in the reference-currency-holding country; Conversely, there is a beggar-thy-neighbor effect when the shock takes place in the other country. In general, the inflation-targeting interest rate rule leads to greater welfare in both countries.

本篇文章的目的為，在一個含有銀行信用管道以及兩種家計單位設定的動態隨機一般均衡模型的架構之中，探討中央銀行實施貨幣政策以及技術面衝擊對於貧富不均度的影響。本篇文章主要依據Kumhof, Rancière and Winant (2015)對於兩種家計單位之設定，參考Benigo and Eggertsson (2016)加入銀行信用管道，並參考Lansing and Markiewicz (2016)將勞動內生化以及刻劃收入來源之不同，因而建構出一個封閉經濟體系，內含兩種不同的家計單位、商品生產部門、銀行信用管道、政府之課稅政策以及中央銀行之貨幣政策。本文發現，貧富不均度在面對中央銀行實施緊縮性貨幣政策以及技術面正向衝擊時會暫時性地擴大，在長期時會回到初始的靜態均衡值。 / The main purpose of this paper is to discuss the effect of monetary policy on income inequality using a micro-based dynamic stochastic general equilibrium model with credit channel and two groups of households. Following Kumhof, Rancière and Winant (2015), households can be divided into two groups; moreover, we follow Benigo and Eggertsson (2016) to add the credit channel, and follow Lansing and Markiewicz (2016) to make households supply labor endogenously and characterize the difference of income source. Therefore, we build up a closed economy model with two groups of households, goods firms, credit channel, the taxation policy implemented by government and monetary policy implemented by central bank. We find that contractionary monetary policy and positive technology shock will temporarily generate a worse income inequality. In the long term, the economy will be back to the initial steady state.

2011年，美國政府在經歷次級房貸和高軍事支出的雙重壓力下，爆發高度財政赤字的問題，造成歐巴馬政府面臨調高債務比例與債務上限的壓力。然而，在眾多的輿論聲中，美國民主黨與共和黨在八月底達成下列協議，減少政府支出、提高債務比例以及增加債務上限等；但是，是否這些方式將改善美國經濟？本篇文章在動態隨機一般均衡(DSGE)架構下，建立一個封閉經濟體系，並將政府支出加入私人廠商部門，透過公共投資，幫助私人廠商增加產出；並且在政府僅採行公債和徵稅融通下，找出一個最適的債務持有比例，使國內福利為最高。而本文發現政府進入生產部門時，將影響最適債務持有比例。即是，隨著政府支出生產彈性越大，最適債務持有比例也會上升，而在基準參數下，我們將會得到最適債務持有比例為百分之十的結論。 / In 2011, under the pressure of subprime mortgage and high military expenditure, the U.S. government accumulated high fiscal deficit, and the Obama government faced the pressure of raising debt ratio and raising debt ceiling. However, among the huge debates, the Republican Party and Democratic Party reached the deal in August which included cut-down government expenditure, raise debt ratio, raise debt ceiling, and so on. But, will these ways improve the U.S. economy? This paper follows the dynamic stochastic general equilibrium (DSGE) framework to construct a closed economy, which the government helps private firm to production through public investment. Besides, given that government only undertakes debt financing and tax financing, we try to find an optimal debt ratio which makes the highest domestic welfare. In our finding, if the government enters private production sector, the optimal debt ratio will be influenced. That is, the optimal debt ratio will increase with the production elasticity of government expenditure. Under the benchmark parameter, the optimal debt ratio is 10 percent.

在面臨2008年金融危機後嚴峻之需求面衝擊下，多國央行紛紛調降利率，甚至調降至零利率，以期望國家能盡速脫離經濟衰退。在利率調降的過程中，由於受零利率下限的限制，單純藉由傳統貨幣政策之調控，仍可能無法使經濟從嚴峻的需求面衝擊下恢復。因此，非傳統貨幣政策也在美國、日本、英國、歐元區等國家被央行所採行做為對抗經濟衰退的政策工具。在此背景下，我們想了解如何實施最適非傳統貨幣政策。 在最適貨幣政策理論發展中，最適傳統貨幣政策發展較早，因此也較為完備。而在最適非傳統貨幣政策方面，前瞻指引(forward guidance)這項政策工具已被引入最適理論中來進行討論，但量化寬鬆(quantitative easing)直至今日還未被引入最適理論中來討論。 因此，本文建構一個封閉的新興凱因斯模型(New Keynesian)，開創性的將量化寬鬆引入最適貨幣政策理論中，來討論最適傳統與非傳統貨幣政策，也藉此與過去文獻比較施行量化寬鬆與未施行量化寬鬆之影響。 / After financial crisis occurred in 2008, countries, such as United States of America, United Kingdom, Japan and the euro area, have been mired in slow economic growth, compared with long-term, and have confronted with severe negative demand shocks which can’t be offset by zero interest-rate policy. Under the circumstance where zero lower bound was present, unconventional monetary policy was implemented by central bank of each country to end up the economic recession prospectively. As a result, we are interested in how to implement optimal unconventional monetary policy. The literatures regarding implementing conventional optimal monetary policy under demand shock were developed maturely. Forward guidance, one of unconventional monetary policy, was already developed in field of optimal monetary policy under impacted by demand shock, but quantitative easing has not been conducted in the theory of optimal monetary policy so far. Thus, we construct a close-economy by New Keynesian model to conduct quantitative easing into the theory of optimal monetary policy to discuss the optimal conventional and unconventional monetary policy, and to compare the difference corresponding to the previous literatures which without quantitative easing.

本文的研究目的為，在一個含有房屋及房屋相關貸款的動態隨機一般均衡模型的架構中，比較貨幣政策、財政政策以及總體審慎政策對於房屋價格及房屋相關貸款的穩定效果。本文建構一個經濟封閉體系，其中包含三種不同家計單位、商品生產部門、房屋建商、資本生產部門，並且由政府部門制定相關政策；此模型的特色為，不同家計單位中的借貸行為、名目價格僵固性以及透過房屋價格抵押貸款的限制來刻劃金融摩擦。我們考慮了一般緊縮貨幣政策、提高財產稅率以及緊縮貸款價值比；本文發現，在三種政策中，對於抑制房屋價格以及降低住房貸款對國內生產毛額的比例，財政政策及總體審慎政策比起緊縮貨幣政策擁有較好的效果。 / The main purpose in this paper is to compare the effect of monetary policy, fiscal policy and macroprudential policy on housing price and housing related loans using a micro-based dynamic stochastic general equilibrium (DSGE) model with housing and housing related loans. We equip a closed economy model with three types of infinitely-lived households (patient households, impatient households and renters), a goods firm, housing and capital producer and a government sector. The model features borrowing and lending between patient and impatient households, nominal rigidity in goods price and financial friction in the form of collateral constraints tied to price of house. We consider the contractionary monetary policy by raising the interest rate, fiscal policy by increasing property tax rate and the macroprudential policy through tightening the loan-to-value (LTV) ratio. We find that among these three policies, in terms of dampening the price of housing and lowering the loan-to-GDP ratio, raising the property tax and lowering the LTV ratio outperforms the contractionary monetary policy.

本研究建構一社會網路互動下的新凱因斯動態隨機一般均衡模型，探討效用基礎下波茲曼分配背後的網路結構，以及，社會網路對新凱因斯動態隨機一般均衡模型參數的影響。根據本論文模擬結果，效用基礎下波茲曼分配背後所隱含的社會網路結構呈現局部區域性連結拓璞，此結論與熱力學對波茲曼分配中粒子互動方式的假設相同，然而，區域性連結之網路結構（如環狀網）並非目前實證研究所觀察到的網路型態（如冪分布網路或高群集係數之小世界網路），故吾人是否得以直接利用效用基礎下波茲曼分配來描述社會上人與人之間的互動現象必需更忱慎考量之。另外，社會網路互動也將使新凱因斯動態隨機一般均衡模型之參數估計產生偏誤，依本研究估計結果觀之，只要加入社會互動，總合需求曲線中實質利率之參數估計將為正號，即實質利率對產出缺口的影響為負向影響，也就是文獻上的投資儲蓄迷思(IS puzzle)，若進一步觀察社會網路結構對該實證迷思的影響則可發現當社會網路群聚程度越高時，該估計偏誤將越嚴重。 / We construct a social network-based New Keynesian DSGE (Dynamic Stochastic General Equilibrium) Model to investigate the underlying social network structure derived from the performance-based Boltzmann-Gibbs model, and thus interpret the process that social network structures affect the estimation bias in the New Keynesian DSGE framework. According to our simulation results, the underlying social network structure derived from the performance-based Boltzmann-Gibbs model should be local. This finding is consistent with the study of thermodynamics, which the Boltzmann-Gibbs distribution is based upon, i.e. the local interaction. However, it contradicts not only the purpose of combining the performance-based Boltzmann-Gibbs machine and New Keynesian DSGE model, but also empirical studies of social network structures in the real world. Accordingly, maybe we have to consider further whether the performance-based Boltzmann-Gibbs machine is a suitable tool for calibrating social interaction under the stylized New Keynesian DSGE framework. Furthermore, if we embedded interaction behavior in the stylized New Keynesian model, the so-called “IS Puzzle” can be consequently observed. We also realized that “IS Puzzle” is connected with network structures. The more clustering the network structure is, the more significant “IS Puzzle” would be.

有鑑於歐洲各國的福利政策與福利支出相較於其他國家高，歐洲國家多會提供窮困與殘障的人民最基本的社會保障，一般人民亦可享受到基礎醫療保障，在失業時也可以領取失業補助；歐洲各政府甚至會收購即將倒閉的企業或者提供補助使企業能夠繼續經營。然而在持續延燒的歐債危機下，為維持歐元區普遍的薪資和福利水平，歐元區內國家開始採取了國家借貸的做法，但由於國際經濟形勢不佳，歐元區經濟增量未達預期，許多國家原有債券陸續到期，若無法借到新貸款，國家將面臨倒閉危機。因此本論文主要以動態隨機一般均衡模型(DSGE)，探討一個封閉經濟體系下，政府支出進入家計單位效用函數後，換言之政府支出變動將會影響家計單位消費的邊際效用，試著尋找能夠極大化社會福利的政府公債占國內生產毛額的最適比例。我們發現在提高政府公債占國內生產毛額比例時：家計單位將預期未來稅賦繳納之金額更高，因而減少消費、增加儲蓄，所以會排擠掉部分私人消費；同時政府必須提撥部分費用以支付債券利息，所以將排擠掉部分政府支出。另外隨政府公債占國內生產毛額比率上升，整體社會福利水準會逐漸下降；因此，我們認為最適政府公債占國內生產毛額比率應為零。 關鍵字：動態隨機一般均衡模型、政府支出、邊際效用、公債、國內生產毛額、社會福利水準 / In Euro zone, large spending obligations needed to support the welfare state and redistribute wealth in an effort to gain greater equality. Most European countries provide liberal social security benefits to the poor, disabled, basic medical needs and very liberal unemployment benefits. They also own and run large public companies. Under the ongoing Euro debt crisis, European governments figure out the way to maintain the high welfare level by increasing the public debt they hold. In our paper, we would like to investigate the optimal ratio of public debt to GDP by constructing a micro-based dynamic stochastic general equilibrium model (DSGE) under a closed economy. We focus on discussing the optimal ratio of public debt to GDP which maximizes social welfare in economy while putting the government expenditure into households’ utility. That is to say, the government expenditure will influence the marginal utilities of households. We find out that as a government decides to raise the debt to GDP ratio; it will crowd out both private consumption and government expenditure. Because households will expect to pay more tax in the future, they will decrease their consumption and increase their saving; high debt ratio means government should have paid more interest payment in the future. Also as the ratio of public debt to GDP rises, the social welfare becomes lower. Thus, in our findings, the optimal debt ratio to GDP should be 0. Keywords: DSGE, Government expenditure, Marginal utility, Public debt, GDP, Social welfare