基于时间约束的多源多品种随机配送系统模型

在基于时间竞争的随机需求环境下,配送系统设计除了使系统总费用的期望值最小外,还要考虑系统稳定性和服务水平等方面的要求。在说明了建模的假设条件后,建立了考虑随机需求和时间约束的多源配送系统随机模型。通过等价变换,将随机模型转化为确定性等价问题,从而方便了问题的求解。     

A TWO FACTOR MODEL OF INCOME DISTRIBUTION DYNAMICS

This paper analyzes empirical income distributions and proposes a simple stochastic model to explain the stationary distribution and deviations from it. Using the individual tax returns data in the U.S. and Japan for 40 years, we first summarize the shape of the income distribution by an exponential decay up to about the 90th percentile and a power decay for the top 1 percent. We then propose a minimal stochastic process of labor and asset income to reproduce the empirical characteristics. In particular, the Pareto exponent is derived analytically and matched with empirical statistics.     

Small noise asymptotics for a stochastic growth model

We develop analytic asymptotic methods to characterize time-series properties of nonlinear dynamic stochastic models. We focus on a stochastic growth model which is representative of the models underlying much of modern macroeconomics. Taking limits as the stochastic shocks become small, we derive a functional central limit theorem, a large deviation principle, and a moderate deviation principle. These allow us to calculate analytically the asymptotic distribution of the capital stock, and to obtain bounds on the probability that the log of the capital stock will differ from its deterministic steady-state level by a given amount. This latter result can be applied to characterize the probability and frequency of large business cycles. We then illustrate our theoretical results through some simulations. We find that our results do a good job of characterizing the model economy, both in terms of its average behavior and its occasional large cyclical fluctuations.     

Large time and small noise asymptotic results for mean reverting diffusion processes with applications

Summary. We use the theory of large deviations to investigate the large time behavior and the small noise asymptotics of random economic processes whose evolutions are governed by mean-reverting stochastic differential equations with (i) constant and (ii) state dependent noise terms. We explicitly show that the probability is exponentially small that the time averages of these process will occupy regions distinct from their stable equilibrium position. We also demonstrate that as the noise parameter decreases, there is an exponential convergence to the stable position. Applications of large deviation techniques and public policy implications of our results for regulators are explored. Received: December 7, 1998; revised version: October 25, 1999     

Politics and the UK's monetary policy

This paper examines whether politics causes regime shifts in deviations from the optimal monetary policy in the United Kingdom. After using a dynamic stochastic general equilibrium model to construct the welfare-maximizing policy rule and deviations from the optimal Taylor rule, we show that politics does indeed play an important role in explaining these deviations. In addition to politics, unemployment rates account for regime shifts in the Taylor rule deviations.     

PRODUCTIVITY AND THE LABOR MARKET: COMOVEMENT OVER THE BUSINESS CYCLE*

The productivity‐driven Mortensen–Pissarides model predicts that labor productivity is strongly correlated with labor market variables whereas these correlations were argued to be much weaker in the data, especially since the 1980s. We first document that the size of these discrepancies between the data and the model becomes substantially smaller if employment data from the Current Population Survey is used in measuring productivity instead of the commonly used employment data from the Current Employment Statistics. Second, we show that incorporating time to build and a stochastic value of home production helps reconcile the quantitative performance of the model with the data.     

Real Exchange Rate Trends and Growth: A Model of East Asia

In contrast to the Balassa–Samuelson hypothesis, many fast-growing Asian countries have experienced little trend real exchange rate appreciation, or even depreciation. Moreover, their long-run real exchange rate trend seems to be dominated by movements in traded goods prices. A model is developed which is consistent with these observations. As in the Balassa–Samuelson model, productivity growth is concentrated in the traded goods sector. Nevertheless the real exchange rate may exhibit trend depreciation, driven by persistent deviations in the price of traded goods from those in the reference country. The key feature of the model is the presence of endogenous productivity growth in the distribution services sector.     

Stochastic investor sentiment,crowdedness and deviation of asset prices from fundamentals

This study constructs a theoretical model to address how stochastic investor sentiment affects investor's crowdedness, and how stochastic investor sentiment and crowdedness affect asset prices. An asset pricing model incorporating stochastic investor sentiment and crowdedness is developed, which can provide efficient explanations for the deviations of asset prices from fundamentals and the maverick risk of investors. This model indicates that the optimistic (pessimistic) investor sentiment and the long (short) crowdedness caused by optimistic (pessimistic) sentimental investors can push asset price above (below) fundamental value. Also, the sentimental investors who are wrong and alone would take the maverick risk. Our results are consistent with the idea that investor sentiment and investor behavior matter for the asset prices and the deviations of asset prices from fundamentals.     

Government extraction and firm size: Local officials’ responses to fiscal distress in China

This paper studies how government extraction behaviors respond to local fiscal distress in China. We exploit the 2002 Chinese Income Tax Reform which exogenously cut local government revenues from income taxes roughly by half. We find that, when facing fiscal distress, local officials resort to informal taxes, such as fees and levies, instead of formal taxes to supplement revenue. On average, the increase in informal taxes recovered 75 percent of the local government revenue loss due to the reform. The increases are more pronounced along the intensive margin and are primarily driven by more extractions from large firms. We also find that the reform led to reductions in investment and growth rates of small firms and consistently more small firms in the total size distribution.     

Modelling the dynamics of Bitcoin and Litecoin: GARCH versus stochastic volatility models

We examine and compare a large number of generalized autoregressive conditional heteroskedastic (GARCH) and stochastic volatility (SV) models using series of Bitcoin and Litecoin price returns to assess the model fit for dynamics of these cryptocurrency price returns series. The various models examined include the standard GARCH(1,1) and SV with an AR(1) log-volatility process, as well as more flexible models with jumps, volatility in mean, leverage effects, t-distributed and moving average innovations. We report that the best model for Bitcoin is SV-t while it is GARCH-t for Litecoin. Overall, the t-class of models performs better than other classes for both cryptocurrencies. For Bitcoin, the SV models consistently outperform the GARCH models and the same holds true for Litecoin in most cases. Finally, the comparison of GARCH models with GARCH-GJR models reveals that the leverage effect is not significant for cryptocurrencies, suggesting that these do not behave like stock prices.     

The law of one price revisited: How do goods market frictions generate large and volatile price deviations?

This paper analyzes the role of goods market frictions in accounting for the large and volatile deviations from the Law of One Price (LOP) in a framework of flexible prices. We draw a distinction between the goods market frictions that are required to consume tradable goods (e.g., distribution costs) and those that are necessary for international transactions (e.g., trade costs). We find that trade costs generate LOP deviations by introducing a no-arbitrage band, while distribution costs cause the price to deviate from the LOP by affecting the probability that trade will occur, given the band. We then conduct a Monte Carlo simulation to show that real exchange rate volatility is positively associated with trade costs, but negatively related to distribution costs. This effect depends on the interplay of trade costs and distribution costs, as they work in opposite directions when creating arbitrage opportunities.     

The Fatter the Tail, the Fatter the Climate Agreement

International climate negotiations take place in a setting where uncertainties regarding the impacts of climate change are very large. In this paper, we examine the influence of increasing the probability and impact of large climate change damages, also known as the ‘fat tail’, on the formation of an international mitigation agreement. We systematically vary the shape and location of the distribution of climate change damages using the stochastic version of the applied game-theoretical STACO model. Our aim is to identify how changes to the distributional form affect the stability of coalitions and their performance. We find that fatter upper tails increase the likelihood that more ambitious coalitions are stable as well as the performance of these stable coalitions. Fatter tails thus imply more successful, or ‘fatter’, international climate agreements.     

Optimal cartel trigger price strategies

A dynamical model of industry equilibrium is described in which a cartel deters deviations from collusive output levels by threatening to produce at Cournot quantities for a period of fixed duration whenever the market price falls below some trigger price. In this model firms can observe only their own production level and a common market price. The market demand curve is assumed to have a stochastic component, so that an unexpectedly low price may signal either deviations from collusive output levels or a “downward” demand shock.     

DO INVESTMENT‐SPECIFIC TECHNOLOGICAL CHANGES MATTER FOR BUSINESS FLUCTUATIONS? EVIDENCE FROM JAPAN

The observed decline in the relative price of investment goods to consumption goods in Japan suggests the existence of investment‐specific technological (IST) changes. We examine whether IST changes are a major source of business fluctuations in Japan, by estimating a dynamic stochastic general equilibrium model using Bayesian methods. We show that IST changes are less important than neutral technological changes in explaining output fluctuations. We also demonstrate that investment fluctuations are mainly driven by shocks to investment adjustment costs. Such shocks represent variations of costs involved in changing investment spending, such as financial intermediation costs. We find that the estimated series of the investment adjustment cost shock correlates strongly with the diffusion index of firms' financial position in the Tankan (Short‐term Economic Survey of Enterprises in Japan). Therefore, we argue that the large decline in investment growth in the early 1990s was due to an increase in investment adjustment costs stemming from firms' financial constraints after the collapse of Japan's asset price bubble.     

A Q-theory model with lumpy investment

We present an analytically tractable dynamic stochastic general equilibrium model that incorporates micro-level fixed and convex adjustment costs. We provide an explicit characterization of equilibrium dynamics by a system of nonlinear stochastic difference equations. We provide general conditions under which our model features investment lumpiness at the microeconomic level, but aggregate dynamics are isomorphic to those in a Q-theory model without fixed costs. This theoretical result is independent of the specification of the fixed cost distribution and also holds true when firms face persistent idiosyncratic productivity shocks.     

The effect of feedback consistency on success in markets with positive feedbacks

In this paper, we show how the finite time expected outcomes in a stochastic ball and urn model depend on the variation in feedbacks by applying the concept of second order stochastic dominance to the feedback distribution. We find that less variation leads to greater expected outcomes.     

Modeling the behaviour of inflation deviations from the target

This study tests for and models non-linearities in inflation deviations from the target in five OECD countries that adopted inflation targeting over the 1990s. Our tests reject the linearity hypothesis and we show that the exponential smooth transition autoregressive (ESTAR) model is capable of capturing the non-linear behavior of inflation misalignments. The extent of inflation deviations from the target varies across the OECD countries, with countries that consistently undershoot the target having a rapid adjustment process, whereas countries that overshoot the target have a slower revision back to equilibrium. Out-of-sample forecasts from the ESTAR model outperform the Markov regime-switching model.     

Social Security Benefit Uncertainty under Individual Accounts

Social Security reforms that include individual accounts change both the expected benefit and the benefit risk. This article uses a long-term stochastic forecasting model to estimate the distribution of expected benefits under a simple individual account, recognizing uncertainties in the current system. Introducing individual accounts increases the overall variability of benefit levels relative to current law; indeed the standard deviations of expected benefit gains exceed the level of those gains. The increase in uncertainty about benefit replacement rates is even larger, however, because individual accounts partially sever the link between earnings and benefits in the existing system. (JEL H55)     

Amenity driven price effects and conservation reserve site selection: A dynamic linear integer programming approach

Most conservation reserve design models presented in the literature are static and ignore the dynamic economic aspects of site selection. Typically conservation programs operate under time-related (e.g. annual) budgets and purchase land over time in a sequential manner. The uncertainty of land development has been incorporated in a few dynamic reserve selection formulations using stochastic dynamic programming. However, the existing formulations do not explicitly deal with inter-temporal price and location linkages. We address this issue here and present a two-period linear integer programming model for conservation reserve design that incorporates amenity driven price feedback effects inherent in the reserve development problem. In addition, the model includes spatial and ecological criteria. We then use this model to answer the question “How suboptimal is ignoring amenity driven price effects in reserve design models?” We apply the model to artificially generated data sets and compare the results with the results of an iterated static model that considers only one period at a time. We find that the dynamic model with price feedback effects selects sites at a lower per-site cost. The policy implication of this finding is that conservation programs should avoid purchasing land in the same neighborhood over multiple time periods.     

Multi-product firms and business cycle dynamics

Recent empirical evidence provided by Bernard et al. (2010) and Broda and Weinstein (2010) shows that a significant share of product creation and destruction in U.S. industries occurs within existing firms and accounts for an important share of aggregate output. In the present paper, and consistent with this evidence, we relax the standard assumption of mono-product firms in a dynamic stochastic general equilibrium model. Our analysis is based on a model of firm dynamics with two deviations from the conventional real business cycle framework—imperfect competition with endogenous entry and multi-product firms. The combination of these two features enables our model to successfully generate a mechanism that accounts for the strong procyclicality of product creation. Due to the proliferation effect induced by firm-level adjustments in product scope, we show that our model embodies a quantitatively important magnification mechanism of aggregate shocks.