DMP Model Research Articles

Autumn phenology consistently delays in subtropical forests in China based on a new process-based model integrating temperature, photoperiod and precipitation

Abstract Climate warming has delayed vegetation autumn phenology, which in turn influences terrestrial carbon and water cycles and their feedback to the climate. However, the performance of autumn phenology models, especially for subtropical forests, remains poor. In this study, we extracted the end-of-photosynthetic-growing-season (EOPS) dates in subtropical China over the period 2001-2018 based on high-resolution solar-induced chlorophyll fluorescence (SIF) dataset using three fitting methods. We developed a new autumn phenology model (DMP model) that integrates precipitation and photoperiod into the classic cold-degree days model, and the new model outperformed the classic model reducing the RMSE by approximately 2 days. We found that the EOPS date was delayed by an average of 4.1 days per decade in the subtropical forests of China from 2001 to 2018, and the precipitation (partial correlation coefficient, r = 0.45), rather temperature (r = 0.29) determined the EOPS processes. We further studied future EOPS using the DMP model and found the EOPS will delay by 1.0 days per decade under the SSP2-4.5 scenario and 2.7 days per decade under the SSP5-8.5 scenario from 2030 to 2100. Our study highlighted the role of precipitation in regulating EOPS in the subtropical forests of China and provided valuable insight for integrating multiple climatic determinants into autumn phenology models.

Income taxation and job creation

AbstractThis paper augments the DMP model with large firms and intrafirm wage bargaining by an endogenous decision to become an entrepreneur that is based on heterogeneous entrepreneurial abilities. If workers’ wage bargaining power is not too large and the match efficiency is not too low, the decentralized market equilibrium features an inefficiently high number of entrepreneurs, because they appropriate large parts of the surplus from matches. A realistic calibration with empirically plausible parameters shows this case to be the relevant one. Consequently, introducing a tax on the profits of entrepreneurs restores the constrained first-best allocation by affecting occupational choices. It drives rather unproductive entrepreneurs out of the market since the marginal entrepreneur is affected and not the average one. Thus, the negative effects on job creation are small.

Jobs and Matches: Quits, Replacement Hiring, and Vacancy Chains and Vacancy Chains

In the canonical DMP model of job openings, all job openings stem from new job creation. Jobs denote worker-firm matches, which are destroyed following worker quits. Yet, employers classify 56 percent of vacancies as quit-driven replacement hiring into old jobs, which evidently outlived their previous matches. Accordingly, aggregate and firm-level hiring tightly track quits. We augment the DMP model with longer-lived jobs arising from sunk job creation costs and replacement hiring. Quits trigger vacancies, which beget vacancies through replacement hiring. This vacancy chain can raise total job openings and net employment. The procyclicality of quits can thereby amplify business cycles. (JEL E24, E32, J23, J31, J63)

Monetary Policy, Trend Inflation, and Unemployment Volatility

AbstractThe literature has long agreed that the DMP model (after Diamond 1982, Mortensen 1982, Pissarides 1985) with search and matching frictions in the labor market can deliver large volatilities in labor market quantities, consistent with empirical data, only if there is at least some wage stickiness. I show, however, that the model can deliver nontrivial volatilities without wage stickiness, as long as it has price dispersion and nonzero long‐run inflation rates. I find that by keeping inflation at a positive rate, monetary policy may be accountable for the large standard deviations observed on labor market variables. In addition, the Shimer (2005) puzzle disappears under monetary policy shocks.

A DMP model of intercity trade

Job matching, a central feature of DMP theory, requires contacts between prospective employers and employees. This paper assumes that they may be either face-to-face and take place at city centers or via referrals from social contacts. The paper presents a model of an economy whose urban structure consists of cities of different types. All cities produce a non-tradeable final good using ranges of tradeable intermediate varieties. Each city has an internal spatial structure: individuals commute to the CBD in order to work, when employed, and to seek jobs, when unemployed. Hiring by each intermediate producing firm is subject to frictions, which are modeled in the Diamond–Mortensen–Pissarides fashion. City type is conferred by specialization in producing one of two types of intermediate varieties and there is intercity trade in intermediate varieties. The paper examines properties of equilibrium with intercity trade and its dependence on various parameters and their consequences for unemployment, output and welfare across the economy along a steady state. The model's use of international trade tools confers a central role to labor market tightness, akin to factor intensity. A natural dependence of unemployment on city size is generated. Equilibrium outcomes generically diverge from the planner's optimum: there exists mismatch generically. Socially optimal unemployment trades off the probability of employment to search costs of firms independently for each skill type and independently of city size. Socially optimal city sizes are independent of the matching model and therefore labor market tightness considerations but reflect both market size effects and the skill composition of the economy.

Epistemic Contributions of Models: Conditions for Propositional Learning

This article analyzes the epistemic contributions of models by distinguishing three roles that they might play: an evidential role, a revealing role and a stimulating role. By using an account of learning based on the philosophical understanding of propositional knowledge as true justified belief, the paper provides the conditions to be fulfilled by a model in order to play a determined role. A case study of an economic model of the labor market—the DMP model—illustrates the usefulness of these conditions in articulating debates over the epistemic contributions of a given model.

Orientation measurement based on magnetic inductance by the extended distributed multi-pole model.

This paper presents a novel method to calculate magnetic inductance with a fast-computing magnetic field model referred to as the extended distributed multi-pole (eDMP) model. The concept of mutual inductance has been widely applied for position/orientation tracking systems and applications, yet it is still challenging due to the high demands in robust modeling and efficient computation in real-time applications. Recently, numerical methods have been utilized in design and analysis of magnetic fields, but this often requires heavy computation and its accuracy relies on geometric modeling and meshing that limit its usage. On the other hand, an analytical method provides simple and fast-computing solutions but is also flawed due to its difficulties in handling realistic and complex geometries such as complicated designs and boundary conditions, etc. In this paper, the extended distributed multi-pole model (eDMP) is developed to characterize a time-varying magnetic field based on an existing DMP model analyzing static magnetic fields. The method has been further exploited to compute the mutual inductance between coils at arbitrary locations and orientations. Simulation and experimental results of various configurations of the coils are presented. Comparison with the previously published data shows not only good performance in accuracy, but also effectiveness in computation.

DMP model

Peter Diamond, Dale Mortensen and Christopher Pissarides won the 2010 Nobel Prize in Economic Sciences for their contribution to the analysis of markets with search frictions, especially when it comes to employment. They created the DMP model, named after the first letters of their last names. Today this is an analytical instrument most used for analyzing unemployment, formation of wages and job vacancies.

DMP model

In 2010 Peter Diamond, Dale Mortensen and Christopher Pissarides won the Nobel Prize in Economic Sciences for their contribution to the analysis of markets with search frictions, especially when it comes to employment. They created the DMP model, named after the first letters of their last names. Today this is an analytical instrument most used for analyzing unemployment, formation of wages and job vacancies.

DMP model

In 2010 the Nobel Prize in Economic Sciences was awarded to Dale Mortensen, born in 1939 in Oregon, USA. He majored in economics and mathematics, and defended his doctoral dissertation at Northwestern University. He was a researcher and professor for full 47 years, having authored numerous papers, either by himself or in cooperation with other scientists. In addition to Mortensen, the 2010 Nobel Prize was also awarded to Peter Diamond and Christopher Pissarides for their contribution to the analysis of markets with search frictions, especially when it comes to employment. They created the DMP model, named after the first letters of their last names. Today this is an analytical instrument most used for analyzing unemployment, formation of wages and job vacancies. This model can be used to assess the impact of various factors of the labor market on unemployment, wages and job vacancies. The concerned Nobel Prize winners formulated the theoretical framework for markets with search friction. Diamond performed the analysis of such markets' foundations; Mortensen and Pissarides expanded this theory and applied it on the labor market. The model designed by these laureates helps us realize how regulations and economic policy affect unemployment, job vacancies and wages. This may refer to the amount of unemployment benefits, or certain regulations in respect of hiring and dismissing people. One of the conclusions is that more generous benefits for unemployed people result in higher unemployment rates and longer job search. In addition to the labor market, the search friction theory may be applied in many other fields, especially at the real estate market.

Solving the DMP Model Accurately

An accurate global algorithm is critical for quantifying the dynamics of the Diamond-Mortensen-Pissarides model. Loglinearization understates the mean and volatility of unemployment, overstates the unemployment-vacancy correlation, and ignores impulse responses that are an order of magnitude larger in recessions than in booms. Although improving on loglinearization, the second-order perturbation in logs also induces large errors. We demonstrate these insights in the context of Hagedorn and Manovskii (2008). Once solved accurately, their small surplus calibration fails to explain the Shimer (2005) puzzle. While the volatility of labor market tightness is close to the data, the unemployment volatility is too high.

Markets with Search Friction and the DMP Model

Dale T. Mortensen delivered his Prize Lecture on 8 December 2010 at Aula Magna, Stockholm University.(This abstract was borrowed from another version of this item.)

Labor Market Monopsony

There has been a renewed interest in monopsony in labor markets in recent years that includes both the traditional static approach to monopsony, ably reviewed by Boal and Ransom (1997), and the “new” approach to monopsony with more attention paid to dynamic issues, developed in detail by Manning (2003). The articles presented in this supplement highlight both approaches and illustrate the range of labor market settings in which the exercise of monopsony power may be important. The first use of the term “monopsony” in economics is widely attributed to Robinson (1969). Robinson conceived of monopsony as analogous to monopoly. Whereas monopoly refers to the case of a single seller confronted in a market by many buyers, monopsony refers to the case of a single buyer confronted in a market by many sellers. Just as the monopolist faces a downward-sloping demand curve for his product and

Vibrational states and optical transitions in hydrogen bonds

Proton energies in hydrogen bonds are mostly calculated using a double Morse potential (the DMP model). This form, however, does not reproduce the experimentally observed correlation between the proton stretching frequency and the bond length in an extended bond-length region sufficiently well. An alternative potential is proposed in the present paper. The quantum states of this non-symmetric double-well potential are calculated numerically using the Numerov (Fox-Goodwin) algorithm. It is shown that the optical spectra of hydrogen bonds in various substances can be well approximated on the basis of the transition frequencies and intensities predicted by the present model. For weakly interacting OH impurities in , the overtone spectrum and line intensities are well reproduced, whereas the line broadenings and the decrease of the fundamental stretching frequencies in intermediate and strong hydrogen bonds are traced back to the influence of the reduced height of the central barrier. The model is also extrapolated to the range of symmetric hydrogen bonds, and the calculated transition frequencies are discussed with respect to most recent infra-red experiments on ice under strong compression. A possible artificial infra-red signal from strained diamond anvils is thereby noted.