Zipf's Law for Cities and Beyond: The Case of Denmark

Zipf's law for cities is one of the most conspicuous and robust empirical facts in the social sciences. It says that for most countries, the size distribution of cities must fit the power law: the number of cities with populations greater than S is inversely proportional to S. The present paper answers three questions related to Zipf's law: (1) does the Danish case refute Zipf's law for cities?, (2) what are the implications of Zipf's law for models of local growth?, and (3) do we have a Zipf's law for firms? Based on empirical data on the 61 largest Danish cities for year 2000, the answer to (1) is NO—the Danish case is not the exception which refutes Zipf's law. The consideration of (2) then leads to an empirical test of (3). The question of the existence of Zipf's law for firms is tested on a sample of 14,541 Danish production companies (the total population for 1997 with 10 employees or more). Based on the empirical evidence, the answer to (3) is YES in the sense that the growth pattern of Danish production companies follows a clean rank‐size distribution consistent with Zipf's law.     

The economic performance of cities: A Markov-switching approach

This paper examines the determinants of employment growth in metro areas. To obtain growth rates, we use a Markov-switching model that separates a city's growth path into two distinct phases (high and low), each with its own growth rate. The simple average growth rate over some period is, therefore, the weighted average of the high-phase and low-phase growth rates, with the weight being the frequency of the two phases. We estimate the effects of a variety of factors separately for the high-phase and low-phase growth rates. Growth in the high phase is related to both human capital and industry mix, while growth in the low phase is related to industry mix only, specifically, the relative importance of manufacturing. Overall, our results strongly reject the notion that city-level characteristics influence employment growth equally across the phases of the business cycle.     

Macroeconomic implications of mortgage loan requirements: an agent-based approach

It is a well-known fact that the housing market, with its associated mortgage securities, plays a crucial role in modern economies. The recent crisis of 2007, triggered by the U.S. real estate bubble, confirms this key role and suggests the importance of regulating mortgage lending. This paper investigates these issues by designing a housing market with a linked mortgage lending instrument in the Eurace agent-based model. Our results show that the presence of a housing market in the model has relevant macroeconomic implications, driven mainly by the additional amount of endogenous money injected into the economy by new mortgages. This additional money generally helps to support and stabilize aggregated demand, thus improving the main economic indicators. However, if the regulation of mortgage lending is too lax, involving an increase in the debt-service-to-income ratio (DSTI), then the additional supply of mortgages no longer enhances macroeconomic performance, and the stability of the economic system is undermined. Based on a number of recent discussions, a regulation of stock control that targets households’ net wealth (a stock), rather than income (a flow) is designed and analyzed. The results show that regulation of stock control can be combined effectively with DSTI to increase the stability of the housing market and the economy as a whole. Interestingly, the regulation based on stock control also directly affects mortgage distribution among households, avoiding excessive concentration. From a policy perspective, our results suggest that the use of a mild flow control regulation, coupled with a stricter stock control measure, fosters sustainable growth and eases first-time buyers access to the housing market, encouraging homeownership.

     

Learning to save in a voluntary pension system: toward an agent-based model

Mandatory pension systems partially replace old-age income, therefore the government matches additional life-cycle savings in a voluntary pension system. Though the individual saving decisions are apparently independent, the earmarked taxes (paid to finance the matching) connect them. Previous models either neglected the endogenous tax expenditures (e.g. Choi et al., in: Wise (ed) Perspectives in the economics of aging, University of Chicago Press, Chicago, pp 81–121, 2004) or assumed very sophisticated saving strategies (e.g. Fehr et al. in FinanzArchiv Pub Finance Anal 64:171–198, 2008). We create twin models: myopic workers learn (i) from farsighted workers using public information (analytic model) and (ii) also from each other (agent-based model). These models provide more realistic results on saving behavior and the impact of matching on the income redistribution than the earlier models.

     

中国优秀旅游城市体系分析

利用城市体系研究的相关理论和方法,对中国优秀旅游城市体系的等级规模结构和空间结构进行了研究与分析,旨在借此透视以中国优秀旅游城市为代表的中国旅游城市体系的宏观结构;分析得到的有别于一般城市体系的、针对旅游职能的特殊类型城市体系的研究结果,将有助于我国旅游城市的宏观结构调整,促进我国城市旅游的整体发展.     

Studying purchasing specialization in organizations: a multi-agent simulation approach

This paper reports on a series of multi-agent-based simulation experiments. The purpose of these experiments is to investigate how factors like task-complexity, availability of skills and corporate policies determine the degree to which a firm may benefit from a specific, dedicated purchasing department. Particular attention is paid to the purchasing of non-product-related items and services. Among the factors investigated are: corporate purchasing policies, available information, capacity of organizational members and the nature of the various purchasing activities. Preliminary results suggest that most of these factors impact on the degree of involvement of a purchasing department as well as the quality of the purchasing activities carried out. The results show the limits of Purchasing's added value and the importance of organizational learning in that respect.     

The size distribution of cities: An examination of the Pareto law and primacy

This paper examines the Pareto and primacy measures of the size distribution of cities. The mean Pareto exponent for a sample of 44 countries is 1.136, somewhat greater than the exponent of one implied by the rank-size rule. We find that value of the Pareto exponent is quite sensitive to the definition of the city and the choice of city sample size. The significance of non-linear terms in variants of the Pareto distribution also indicate that the rank-size rule is only a first approximation to a complete characterization of the size distribution of cities within a country. The relatively low correlation between primacy and Pareto measures confirms the need for a variety of measures of city size distributions. This paper also suggests that large cities are growing faster than small cities in most of the countries in our sample. This is indicated by the positive coefficient on the first non-linear term introduced into the Pareto equation. Finally, variations in the Pareto exponent and measures of primacy are partly explained by economic, demographic, and geographic factors.     

城市新区规划仿真模型系统分析方法研究

通过应用系统动力学建立城市新区规划系统仿真模型,已成为新区规划的一种重要手段。从分析构建仿真模型过程中通常所采用的系统分析方法入手,阐明了该方法的一些不足之处,提出了一种改进型的分析方法,即系统反馈环分析方法,探讨了该方法的机理和可行性,并结合天津滨海新区空港加工区的案例,论述了该方法对仿真模型系统结构和行为模式的分析过程。     

The impact of social influence in Australian real estate: market forecasting with a spatial agent-based model

Journal of Economic Interaction and Coordination - Housing markets are inherently spatial, yet many existing models fail to capture this spatial dimension. Here, we introduce a new graph-based...     

An agent-based model of the observed distribution of wealth in the United States

Pareto cautiously asserted that the wealth and income distributions which bear his name are universal, basing his argument on observations of this distribution in many different types of economies. In this paper, we present an agent based model (and a scalable approximation of it) in a closely related spirit. The central feature of this model is that wealth enables an individual to secure more wealth. Specifically, the important and novel feature of this model is its ability to simultaneously produce both the Pareto distribution observed in empirical data for the top 10% of the population and the exponential distribution observed for the lower 90%. We show that the model produces these distributions of wealth when initialized with an equitable distribution. Then, using historical data, we initialize the model with US wealth shares in 1988 and show that the model tracks wealth share changes from 1988 to 2012. Simulations to 2088 project that the top 0.01% of the population will possess more than 70% of the total wealth in the economy.     

An agent-based model of innovation diffusion: network structure and coexistence under different information regimes

The paper analyzes how the structure of social networks affects innovation diffusion and competition under different information regimes. Diffusion is modeled as the result of idiosyncratic adoption thresholds, local network effects and information diffusion (broadcasting and demonstration effect from previous adopters). A high social cohesion decreases the probability of one innovation cornering the market. Nonetheless, with imperfect information, in small-world networks the higher speed of diffusion produced by the low average distance increases this probability. A low social cohesion also increases the probability of falling into traps of under-adoption. However, such probability is significantly lower with imperfect information, because such regime is characterized by higher levels of market concentrations and this reduces the frictions due to the coexistence of non-compatible product innovations.     

The distribution of wealth: an agent-based approach to examine the effect of estate taxation,skill inheritance,and the Carnegie Effect

Journal of Economic Interaction and Coordination - Wealth inequality has been a topic of recent interest worldwide. One means to address wealth inequality may be through estate taxation. To study...     

The use of simulation in system design: A case study using the precision location strike system

The purpose of the article is to illustrate the use of computer simulation study and modeling in the design of complex systems. When new systems are designed, decision-makers rely heavily upon judgment, intuition and experience. The method discussed is intended to enhance these executive attributes by providing a vehicle with which the decision-maker may be proactive before implementing the system rather than being solely reactive after implementation.The application of a method known as the “systems science paradigm” is discussed and illustrated using the U.S. Air Force's Precision Location Strike System. The problem was to design a logistical support structure for the Strike System. The three major options proposed were to locate repair and resupply structures at the point of equipment use in Europe, to have a mixed system, or to locate support at a base in the continental United States.The research employed the paradigm suggested to develop an experimental Q-GERT simulation model of the processes and structures envisioned. Data development for abstract systems is illustrated and methods to experiment with alternate structures are developed and discussed. The concept of multiechelon inventory and repair are addressed within the problem's context.A proposed design alternative resulted from application of the process. Methods, other than cost effectiveness, to evaluate the system are also suggested. Implementing the design process for ill-defined systems appears to be an effective method for dealing with such design problems.     

School dropouts in Ontario: A simulation of the phenomenon in a local school system

The article describes a simulation model and some rather lengthy statistical exercises analyzing the high school dropout phenomenon in Ontario and estimating the effect of policy measures which might affect the loss rates. The article is one of a series of dropout studies which have been carried out by the faculty and research staff of the Ontario Institute for Studies in Education since 1972. The earlier ones were surveys. The annual time series data which they established are now being used for simulations such as those reported here.     

Artificial stock markets with different maturity levels: simulation of information asymmetry and herd behavior using agent-based and network models

This paper aims mainly at building artificial stock markets with different maturity levels by modeling information asymmetry and herd behavior. The developed artificial markets are multi-assets, order-driven and populated by agents having heterogeneous behaviors and information. Agents are defined by their information and their herd behavior levels. Agents trade multiple risky assets based on their wealth, their behaviors and their available information which spread among multiple behavioral networks. In a novel contribution to artificial stock markets literature, agents’ behaviors modeling is mixed with social network simulation to reproduce different degrees of information asymmetry and herd behavior based on several assortative topologies. Several simulations validated the proposed model since univariate and multivariate stylized facts were reproduced both for mature and immature stock markets. The proposed artificial stock market can be considered as a first step toward decision and simulation tools for optimal management, strategy analysis and predictions evolution of immature stock markets.     

The process of regionalization: An appropriate conceptual and methodological approach

Socioeconomic planning often necessitates the development of a set of areal units. This spatial component of planning is regionalization, and it must be conceptually and methodologically compatible with its purpose. Many elements common to most traditional procedures (continguity constraints, predetermination of the number or size of regions, and mutual exclusivity of regions) jeopardize the validity of the regionalization. An alternative approach, factorial regionalization, produces intuitively meaningful regional types without imposing unrealistic constraints upon the regional landscape. In addition to being more objective, the procedure yields a greater amount of information than traditional methods. This in turn allows more flexibility in interpreting and employing the results of the regionalization.