新凯恩斯货币政策模型

估计了新凯恩斯主义最优价格模型,并评估利用模型如何描述美国的产出、通货膨胀和利率变动;考虑模型中外在习惯形成是否影响消费者行为,并说明定价方法和通货指数形成价格和通胀惯性。该模型的时间一致均衡原则是用来估计关键行为参数的,据此研究最优货币政策的适应性。     

Global and local determinacy in a one-step forward looking New Keynesian model

In this paper we consider a New Keynesian model for optimal monetary policy in a staggered fashion. We provide the relations of a non linear model of general economic equilibrium, implementing a suitable Taylor-type interest rate rule. We characterize the conditions that guarantee local determinacy and explore conditions under which local bifurcations of the target equilibrium may occur. Afterwards, we argue how local determinacy might be associated with global indeterminacy, providing some numerical examples.     

中国货币政策与财政政策协调机制的均衡分析 ——基于非线性结构模型系统

为探究货币财政政策在既定宏观经济目标下政策协调的最优均衡策略,本文引入内生的政府支出政策,并基于非线性利率及财政赤字率作用的货币供应量方程构建非线性结构模型.进一步地,对包含内生政策的非线性结构模型进行对数线性化处理与参数校准,并基于既定预期目标研究货币政策与财政政策的协调问题.特别地,对2008年和2017年进行了政策均衡模拟分析.通过模拟分析可以发现,当经济出现较大波动时,采用本文模型可以得到满足均衡情况的实际利率和财政赤字率的最优政策组合,与我国当前实际经济采取的政策组合较为一致.     

Optimal interest rate rule in a DSGE model with housing market spillovers

This paper studies the optimal interest rate rule in a DSGE model with housing market spillovers (Iacoviello and Neri, 2010). We find that the optimal rule responds to house price inflation even when the stabilization of house price is not among the objectives of the policymaker, and that the strength of the response depends crucially on a few structural parameters.     

Optimal Monetary Policy

Optimal monetary policy maximizes the welfare of a representative agent, given frictions in the economic environment. Constructing a model with two sets of frictions—costly price adjustment by imperfectly competitive firms and costly exchange of wealth for goods—we find optimal monetary policy is governed by two familiar principles. First, the average level of the nominal interest rate should be sufficiently low, as suggested by Milton Friedman, that there should be deflation on average. Yet, the Keynesian frictions imply that the optimal nominal interest rate is positive. Second, as various shocks occur to the real and monetary sectors, the price level should be largely stabilized, as suggested by Irving Fisher, albeit around a deflationary trend path. Since expected inflation is roughly constant through time, the nominal interest rate must therefore vary with the Fisherian determinants of the real interest rate. Although the monetary authority has substantial leverage over real activity in our model economy, it chooses real allocations that closely resemble those which would occur if prices were flexible. In our benchmark model, there is some tendency for the monetary authority to smooth nominal and real interest rates.     

Optimal monetary policy with the cost channel and monopolistically-competitive banks

This paper studies the optimal nominal policy interest rate in a model with the cost channel and imperfect competition in the banking sector. Due to this market power, the interest rate on deposits is relatively low; in particular it is lower than the policy interest rate. This, in turn, leads to a suboptimal level of deposits and, as a result, to a low level of intermediation. Deviations from the Friedman Rule are optimal in this setup regardless of the assumption about price rigidity; since households can hold their assets in the form of cash or deposits, taxing money, which is an imperfect substitute for deposits, is optimal in order to increase the level of deposits and encourage intermediation. The main results of the paper are robust to the introduction of market power in the loan market as well as stickiness in both the deposit and the loan markets.     

Interest rate rules, inflation and the Taylor principle: an analytical exploration

Summary. The purpose of this article is to characterize optimal interest rate rules in the framework of a dynamic stochastic general equilibrium model, and notably to scrutinize the “Taylor principle”, according to which the nominal interest rate should respond more than one for one to inflation. This model yields explicit solutions for the optimal rule. We find that the elasticity of response depends on numerous factors, such as the degree of price rigidity, the autocorrelation of the underlying shocks, or which measure of inflation is used. In general the optimal elasticity of the interest rate with respect to inflation needs not be greater than one.Received: 6 November 2003, Revised: 17 August 2004 JEL Classification Numbers: E5, E52, E58.J.-P. Bénassy: I wish to thank Daniel Laskar and an anonymous referee for their perceptive comments on earlier drafts of this paper. Of course all remaining deficiencies are mine.     

Stabilizations, crises and the “exit” problem – A theoretical model

Exchange-rate-based stabilizations, even if successful, usually lack credibility initially. This is reflected in high (ex post) real interest rates and some degree of real exchange rate appreciation. Empirical observation suggests that wage inflation declines smoothly over time whilst interest rates are volatile. Our model captures these features and provides insights into: the eruption of exchange rate crises after a long period of apparently successful stabilization; the potential advantages of a heterodox approach; when to delay a stabilization attempt; and the optimal date for “exit” to a floating exchange rate.     

投机资本流入、利率政策的两难问题和货币政策工具的最优搭配

本文构建理论模型分析了如何选择利率和存款准备金率工具的最优搭配,从而在防止通货膨胀和防止热钱流入之间取得最佳平衡。模型显示存款准备金率只对银行贷款起直接抑制作用,当人们通过非银行渠道融资时,可规避准备金率的限制,使其效果下降。而利率政策通过套利机制也对非银行融资起直接限制作用。而且利率政策可以避免对信贷资金分配的不对称限制,使资金分配更平衡有效,所以利率政策相对占优。但当利率吸引投机资本时,可搭配使用准备金率政策以减少利率需要提高的程度,以减少热钱流入。     

Optimal disaster-preventive expenditure in a dynamic and stochastic model

The purpose of this study is to present an analytical framework for publicly optimal disaster-preventive expenditure. We examine the optimal policy combination of tax rate, disaster-preventive expenditure, and productive government expenditure in a neoclassical growth model, in which natural disasters occur stochastically and partially destroy existing capital. Based on this model, we can decompose the welfare effect of raising preventive expenditure into three effects: the damage reduction, crowding out, and precautionary effects. By identifying these marginal benefits and costs, we obtain the policy conditions that maximize household welfare. Furthermore, we show that optimal prevention is increasing in disaster probability, and by using a numerical example, we show that there is an inverse U-shaped relationship between the expected growth rate and disaster probability.     

Vintage capital and the dynamics of the AK model

This paper analyzes the equilibrium dynamics of an AK-type endogenous growth model with vintage capital. The inclusion of vintage capital leads to oscillatory dynamics governed by replacement echoes, which additionally influence the intercept of the balanced growth path. These features, which are in sharp contrast to those from the standard AK model, can contribute to explaining the short-run deviations observed between investment and growth rates time series. To characterize the optimal solutions of the model we develop analytical and numerical methods that should be of interest for the general resolution of endogenous growth models with vintage capital.     

Monetary Policy,Financial Frictions,and Heterogeneous R&D Firms in an Endogenous Growth Model*

Motivated by empirical facts, I construct an endogenous growth model in which heterogeneous research and development (R&D) firms are financially constrained and use cash to finance R&D investments. I also examine the optimal monetary policy. The effects of financial constraint crucially depend on whether R&D firms are homogeneous or heterogeneous regarding R&D productivity. If R&D firms are homogeneous, then the zero nominal interest rate (i.e., the Friedman rule) is always optimal under severe financial constraint. Heterogeneity in R&D productivity leads to the opposite result. With heterogeneity, severe financial constraint makes the strictly positive nominal interest rate welfare-improving under a plausible condition.     

The government deficit in a growth model: Consequences and trade-offs

This paper investigates the consequences of a fixed, positive government deficit/national-income ratio (where the deficit includes interest payments on the debt) in a growth model. To keep the deficit ratio fixed, policymakers must continuously adjust the primary deficit ratio (the deficit ratio when the deficit excludes interest payments) to offset endogenous changes in the interest/income ratio. The model is used to derive the impact of the deficit ratio and the monetization ratio-the fraction of the deficit financed by money-on the capital/labor ratio, the inflation rate, and the interest/income ratio. Consequences and trade-offs are examined. In the model, raising the deficit ratio reduces the capital/labor ratio; and must raise either the interest/income ratio, or the inflation rate, or both.     

Optimal growth in the two-sector neoclassical growth model

This article analyzes optimal growth in the neoclassical two-sector model. First, the optimal savings ratio is derived corresponding to that growth path which maximizes consumption at each point of time. Secondly, it can be shown that this optimal savings ratio is the limit for the optimal savings ratio as derived by Pontryagin's maximum principle for an optimal policy, when the social discount rate for future per capita consumption approaches zero.This work was supported by the Deutsche Forschungsgemeinschaft, West-Germany.     

Financial crises and time-varying risk premia in a small open economy: a Markov-switching DSGE model for Estonia

Under a currency board, the central bank relinquishes control over its monetary policy and domestic interest rates converge towards the foreign rates. Nevertheless, a spread between both usually remains. This spread can be persistently positive due to elevated risk in the economy. This paper models that feature by building a DSGE model with a currency board, where the domestic interest rate is endogenously derived as a function of the foreign rate, the external debt position and an exogenous risk premium component. Time variation in the volatility of the risk premium component is then modelled via a Markov-switching component. Estimating the model with Bayesian methods and Estonian data shows that the economy does not react much to shocks to domestic interest rates in quiet times but is much more sensitive during crises, and matches the financial and banking crises, which cannot be captured by the standard DSGE model.     

Restoring Wetlands Through Wetlands Mitigation Banks

This paper offers the first economic analysis of wetlands mitigation banks. The banks are a new alternative for restoration of wetlands by developers before receiving regulatory approval for future development of wetlands in the same watershed. A stochastic optimal control model is developed which incorporates ecological uncertainty of wetlands restoration. The model helps in examining the decisions of how much to invest in a wetlands mitigation bank. The model is calibrated with data from California bioeconomic parameters. Numerical simulation of the model provides a sensitivity analysis of how model parameters of restoration costs, stochastic biological growth, interest rate, and the market value of credits affect the trajectory of investment and the optimal stopping state of wetlands quality when the investment ends. The analysis reveals that restoration of the whole site will occur when there is a reduction in restoration costs, an increase in biological uncertainty or an increase in the value of wetlands credits. Continued restoration is harder to justify with a higher interest rate.     

Adverse selection as an explanation of credit rationing and different lender types

An adverse selection model is utilized to demonstrate that informational asymmetry may make it wealth optimal for the financial intermediary (FI) to credit ration and to rationalize the existence of different lenders in the credit market. The crucial assumption is that borrowers differ in their tolerance for a lender-imposed default penalty, the severity of which also varies with the lender. The credit rationing portion proves that the FI will: 1) be forced by a binding regulatory constraint to overinvest in capital; 2) ration its worst risk class borrowers; 3) establish its optimal loan interest rate on the basis of the average quality of its loans and the interest rate elasticity of the borrower demand in its best risk category; and 4) decrease the total loan volume and increase the loan interest rate due to an increase in the capital requirement, but the effect on the default risk quality of its loan portfolio is ambiguous. The existence result is that if a lender has a high default penalty, he can charge a lower rate and attract only “good” borrowers, i.e., heterogeneous lender types encourage the screening of borrowers and vice versa.     

Optimal foreign debt for Egypt: A stochastic control approach

This study assesses the foreign debt policy in Egypt and contrasts it versus the optimal policy during the period 1985–2008. It also presents a forecast of the optimal debt during the period 2009–2014. The optimal debt policy was derived using an open economy model for Egypt. The uncertainties in the model stem from the uncertainties in the interest or debt service payments and the uncertainties in the rate of return on investments. The stochastic control approach was used to find the optimal debt policy. It was found that Egypt could borrow externally as long as the trend in the rate of return on investments exceeds the trend in the real interest rate or the trend in the rate of the debt service payments. The analysis finds that Egypt's foreign debt was higher than the optimal level before 1997. After 1997, foreign debt seems to converge to the optimal level. However, Egypt's foreign debt is still below its optimal level which results in an opportunity cost for the economy to grow, otherwise, GDP could have recorded a favorable increase.     

What horizon for targeting inflation?

We investigate optimal horizons for targeting inflation in response to different shocks and their properties. Our analysis is based on a well specified macroeconometric model of Norway. We find that optimal horizons are highly shock-specific and do not increase with concern for output and/or interest rate fluctuations beyond some shock-specific levels. Optimal horizons increase with the degree of persistence in shocks while they are not affected by the size of a shock unless the central bank is averse to interest rate volatility. In the face of multiple shocks, however, sizes as well as signs of shocks become important for optimal horizons even when the central bank is not averse to interest rate volatility. This is because shocks of different signs and sizes may amplify or outweigh each others’ effects.