On the combination of exponential smoothing and diffusion forecasts: An application to broadband diffusion in the OECD area

The innovation diffusion literature has established that the spread of a successful innovation over time typically follows a sigmoid curve. Therefore, the forecasting in this area has been monopolized by the use of well known aggregate diffusion models. Time series forecasting has been surprisingly neglected, as it provides mainly accurate short term forecasts. In this work, a method of exponential smoothing, the Holt's damped trend with a modification, is applied in recent broadband diffusion data of two large regions after the reach of the inflection point. As validated with holdback sample data ranging from 6 up to 30 months, the key for successful forecasting is the use of the estimated saturation level calculated from a diffusion model, in order to specify the appropriate trend. The results indicate improved predictions compared to two popular diffusion models, the Gompertz and the Linear Logistic model. The paper concludes with the application of the proposed method in a 48-month forecasting horizon, as well as the suggestions for further research.     

A simple algebraic estimation procedure for innovation diffusion models of new product acceptance

A simple algebraic estimation procedure is developed to estimate the parameters of diffusion models of new product acceptance. The procedure required knowledge of the occurrence of the point of inflection (based on actual data, analogous products, or management judgments). It is conceptually easy to use and can be implemented by using a hand calculator. Since the procedure does not employ period-by-period time-series diffusion data, it is not expected to provide the best fit to the data as compared to the maximum likelihood and nonlinear least squares estimation procedures. However, the procedure can provide very reasonable estimates about the relative magnitudes of the parameter estimates. In that respect, the procedure can be used to generate good starting values for the maximum likelihood and nonlinear least squares estimation procedures. In the absence of data, using management judgments about the point of inflection, the procedure can be implemented in a decision-support system to develop conditional diffusion curves for a new product. Data from four diverse innovations are used to illustrate the procedure.     

A product diffusion model incorporating repeat purchases

A logistic-based model for forecasting the rate of product diffusion given aggregate time series data was constructed. The model differs from earlier models based on fitting the logistic to aggregate data in that it includes a submodel to separate replacement demand from first-time sales. We fit the theoretical model to data and show that forecasts will be significantly more accurate using this model instead of the logistic curve.     

Adaptive diffusion models for the growth of robotics in New York state industry

Forecasts are developed for the diffusion of robotics in the state of New York through the year 2015. The chief objective is to compare static approaches with dynamic models for forecasting diffusion processes of various time horizons. Results for a Bass-Mansfield model are compared to those for a dynamic time-varying parameter model. The results indicate the advantages and disadvantages of a robust heuristic approach which smooths data as opposed to providing an optimal fit.     

制造业碳排放和经济增长脱钩关系研究——基于速度和数量双重视角

基于速度脱钩和数量脱钩的双重视角,利用Tapio脱钩模型和环境库兹涅茨曲线模型,研究中国1987—2017年制造业碳排放和制造业经济发展的脱钩关系。结果表明:我国制造业2016—2017年、2008—2017年均为弱脱钩状态,制造业经济和碳排放呈倒“N”型关系,2017年制造业经济处于环境库兹涅茨曲线两拐点之间,未发生数量脱钩。借助“环境高山”理论可知,我国制造业处于经济增长和环境保护的“两难境地”,因此,政府需要做好经济和环境政策的长期攻坚准备。     

The automobile in a system context: The past 80 years and the next 20 years

The diffusion of automobiles in nine countries is seen in terms of the Volterra equations developed for ecological systems. Three parameter logistic equations fit the evolution of the car population perfectly. The behavior suggests a quasi-biological, internally generated determinism that belies the significance of engineering, economics, marketing, and media as diffusion stimuli. Their role is seen to be more a response to, than an initiator of, change. Once diffusion is complete, their significance increases, however. Car safety appears to be controlled by societal “set points.”     

团队地位差异性与团队创造力的倒U型关系：任务特征的调节作用

基于互动过程视角，构建团队地位差异性对团队创造力的倒U型影响模型，并通过106个团队455份有效调问卷进行实证检验。结果表明，团队地位差异性对团队创造力存在倒U型影响，在该影响过程中，任务复杂性、任务互依性的调节作用显著，影响二者倒U型关系的拐点位置。随着任务复杂性提高，团队地位差异性对团队创造力的倒U型曲线拐点向左移动，且拐点位置更高；同样地，随着任务互依性提高，二者的倒U型曲线拐点向左移动，且拐点位置更高。     

中国区域环境效率及其影响因素

本文基于DEA方法运用2000—2008年省级面板数据计算了我国30个省市的环境效率,同时使用Tobit模型分析了该环境效率的影响因素。研究表明:(1)2000—2008年,中国30个省区的环境效率基本保持在0.7～1之间波动,各省区平均环境效率刚开始时呈下降趋势,但在2004年或2005年出现明显拐点。(2)我国环境效率地区差异明显,东部发达地区在效率水平上优于中西部地区,中西部地区环境效率的敏感性高。另外,2005年以来西部与东部的效率差距趋于缩小,而中部的情况则不乐观。(3)加大对从业人员、能源、用水等投入要素的利用程度,能有效提高环境效率。(4)经济水平、外贸依存度、人口密度都会对我国环境效率产生显著的正面影响,其中人均GDP和进出口贸易额对环境效率影响较大,而工业污染治理投资占GDP比重对环境效率影响不显著。     

Nonparametric panel estimation of online auction price processes

In this study, we examine the price process of eBay online auctions. We pool sparse and unevenly spaced bidding histories of individual auctions, resulting in an unbalanced panel of bids. Since the price processes of online auctions are monotonically increasing within individual auctions and exhibit a substantial degree of heterogeneity, we propose a monotone series estimator for panel data with auction-specific slopes for a common relative price growth curve. We generalize Ramsay’s (1998, J R Stat Soc B 60(2):365–375) monotone series estimator to fit our panel model of the price process. We apply the proposed model and estimator to eBay auctions of a popular hand-held device (a Palm PDA). The results are shown to capture closely the overall pattern of observed price dynamics. In particular, the early bidding, mid-auction bidding drought, and end-auction bid sniping are well approximated by the estimated price curve.     

Monopoly with local knowledge of demand function

In this note, we propose a model where a quantity setting monopolist has incomplete knowledge of the demand function. In each period, the firm sets the quantity produced observing only the selling price and the slope of the demand curve at that quantity. Given this information and through a learning process the firm estimates a linear subjective demand curve. We show that the steady states of the dynamic equation are critical points of the objective profit function. Moreover, results depend on convexity/concavity of the demand. When the demand function is convex and the objective profit function has a unique critical point: the steady state is a globally stable maximum; conversely when then steady state is not unique, local maximums are locally stable, while local minimums are locally unstable. On the other hand when the demand function is concave, the unique critical point is a maximum: there can be stability or instability of the critical point and period two cycles around it via a flip bifurcation. Moreover, through simulations we can observe that, with a mixed inverse demand function, there are different dynamic behaviors, from stability to chaos and that we have transition to complex dynamics via a sequence of period-doubling bifurcations. Finally, we show that the same results can be obtained if the monopolist is a price setter.     

The fertility effect of dependent tax exemptions: estimates for the United States

Many developed countries allow tax subsidies for families to help reduce the costs of bearing and rearing children. Whittington et al. in 1990 developed a theoretical model in which they estimated the effect of tax deductions for dependent children on fertility in the US. This paper develops an empirical model of estimation and reconsiders Whittington's work. Nonlinear specification of the demand curve for children is central to the new model. This change is made based on the hypothesis that nonlinear specification will better capture the shape of demand. Using annual time-series data over the period 1913-84, the study found the marginal effect of dependent exemptions to decrease with exemption level. Given the historically low recent levels of exemptions in real terms, increasing current exemptions will affect fertility to a greater extent than previously estimated. Graphically, results point to the existence of a concave demand for children.     

A trigonometric flexible consumer demand system

Abstract.  This paper proposes the first ever empirical specification of a trigonometric demand system. The new model is potentially useful because of some attractive features. It is flexible, amenable to exact aggregation over consumers, possessed of trigonometric Engel curves, which can oscillate, and able to have an unusually large regular region. With comparisons between the new model and two other popular models, an illustration is given for Japanese demand for non‐durables and services. The new model shows relatively gentle Engel curves with an inflection point on each of them, which seem reasonable, given that aggregate expenditure is used in parameter estimation. JEL classification: C51, D12     

中国货币化率与经济增长

近年来,中国高货币化率问题愈发严重,学者们专注于寻找其背后的原因,却忽略了对货币化率与经济增长关系的研究.为此,在对货币化率影响经济增长相关理论进行总结归纳基础上,提出货币化率与经济增长之间呈现倒U型关系的理论假设,并且选择全球72个主要国家1996—2018年面板数据,对货币化率与经济增长之间关系进行实证检验.结果表明:在全样本和发达国家子样本中,货币化率与经济增长之间呈现倒U型关系,目前我国货币化率水平小于全样本数据拐点值,大于发达国家子样本数据拐点值.发展中国家子样本数据则显示,货币化率与经济增长呈现正U型关系,适当提高货币化率可以促进经济增长.最后,根据上述结论,提出中国货币化率最优路径图.     

中国城镇化对环境污染的空间溢出与门槛效应研究

基于2000—2017年中国31个省份的面板数据,建立空间面板杜宾模型和面板门槛回归模型,对城镇化与环境污染的关系进行实证分析和相应的政策讨论。结果表明:中国环境污染存在明显的正向空间依赖性和空间异质性,东部地区主要表现为高—高集聚类型,西部地区主要表现为低—低集聚类型;城镇化对环境污染的影响具有显著的空间外溢效应,且区域间的溢出效应大于区域内的本地效应;城镇化与环境污染呈倒"U"型曲线关系,拐点发生在城镇化水平达到86.16%处;城镇化对环境污染的影响存在门槛特征,随着经济规模的扩大,城镇化对环境污染的正向影响逐渐减弱,随着第三产业与第二产业比值的增加,城镇化对环境污染的正向影响先增强后减弱。基于此,提出建立区域环境污染协同治理机制、制定差异化的产业结构调整策略、加强环保技术的研发与推广、积极倡导绿色生活方式等政策建议。     

Income distribution functions with disturbances

Recent exercises in the maximum likelihood estimation of income distribution functions provide goodness of fit tests which lead to the rejection of most models. This result is usually ignored on the ground that the test is too strict, since it allows for sampling variation only. If income distribution functions, like other econometric models, are not meant to hold exactly, we should introduce disturbances in the statistical model. Here we treat observed income as the sum of a systematic component with a specific two-parameter distribution — Pareto, Gamma, or Lognormal — and an independent normal error. The ensuing models fit conventional U.S. income data much better than their traditional counterparts, but they still fail a goodness of fit test.     

Recursive contracts,lotteries and weakly concave Pareto sets

Marcet and Marimon (1994, revised 1998, revised 2011) developed a recursive saddle point method which can be used to solve dynamic contracting problems that include participation, enforcement and incentive constraints. Their method uses a recursive multiplier to capture implicit prior promises to the agent(s) that were made in order to satisfy earlier instances of these constraints. As a result, their method relies on the invertibility of the derivative of the Pareto frontier and cannot be applied to problems for which this frontier is not strictly concave. In this paper we show how one can extend their method to a weakly concave Pareto frontier by expanding the state space to include the realizations of an end of period lottery over the extreme points of a flat region of the Pareto frontier. With this expansion the basic insight of Marcet and Marimon goes through – one can make the problem recursive in the Lagrangian multiplier which yields significant computational advantages over the conventional approach of using utility as the state variable. The case of a weakly concave Pareto frontier arises naturally in applications where the principal?s choice set is not convex but where randomization is possible.     

Automatic smoothing parameter selection: A survey

This is a survey of recent developments in smoothing parameter selection for curve estimation. The first goal of this paper is to provide an introduction to the methods available, with discussion at both a practical and also a nontechnical level, including comparison of methods. The second goal is to provide access to the literature, especially on smoothing parameter selection, but also on curve estimation in general. The two main settings considered here are nonparametric regression and probability density estimation, although the points made apply to other settings as well. These points also apply to many different estimators, although the focus is on kernel estimators, because they are the most easily understood and motivated, and have been at the heart of the development in the field.     

创新扩散时间形态的S型曲线研究

创新扩散是创新通过某种渠道随着时间在社会系统成员间传播的过程。创新扩散S型规则由两条曲线组成：一条被称为累积采用曲线,即S型曲线;另一条被称为单位时间采用量曲线,即钟形曲线。创新扩散率主要受创新特点、创新者特点和环境因素的影响。从创新扩散S型曲线的由来看,其发端于人口增长模型中的增长曲线,后由Tarde提出S型曲线规则,最后Ryan和Gross促使其成为一种研究范式。从创新扩散S型曲线成因看,“波浪效应”和“阈值模型”是两种典型的解释模型：“波浪效应”是指创新扩散过程就像波浪一样,由创新中心点向四周扩散;“阈值模型”探讨了在个人参与某项活动之前,参与该活动的其他个体必须达到的人数。未来重点围绕3个方面进行深化研究：①进一步验证S型曲线;②验证创新扩散S型曲线中的数理模型;③结合创新扩散影响因素与扩散形态,将模型应用到创新扩散预测方面。     

城市的经济发展水平影响空气质量吗——基于中国31个省会城市和直辖市的经验验证

基于库茨涅兹曲线,并考虑到各城市的内生因素的影响,研究我国的经济发展水平和空气质量的关系,实证结果显示,我国省会城市、直辖市的曲线只存在库茨涅兹曲线拐点后面的部分,且倾斜程度十分微小,即表明近十年内,我国省会城市、直辖市的空气质量随着经济的发展,得到一定程度的改善,但是改善程度十分有限,城市的经济发展水平对其空气质量水平并不具有决定性作用,影响城市空气质量的最主要因素来自城市自身及其周边地区的工业排放物。     

STRUCTURAL CHANGE AND NONLINEARITIES IN A PHILLIPS CURVE MODEL FOR SOUTH AFRICA

The main objective of this article is to reexamine the role of the Phillips curve for monetary policy analysis in South Africa by augmenting the model for major structural changes in the balance-of-payments and labor market. The main findings show that a linear Phillips curve with an output gap in levels accurately describes South Africa's nontrended inflation experience during 1971(Q1)–1984(Q4), whereas a piecewise concave curve with an output gap in growth rates correctly predicts the decelerating inflation pattern during 1986(Q1)–2001(Q2). The concave curve after 1985 imparts a deflationary bias that requires expansionary demand-side policies to stabilise the inflation rate. An important corollary is that expansionary demand-side policies can raise the average growth rate of the output gap over time without sacrificing stabilization objectives. (JEL C22, E3, E52 )