A Nonstationary Cylinder–Based Model Describing Group Dispersal in a Fragmented Habitat

□ A doubly nonstationary cylinder-based model is built to describe the dispersal of a population from a point source. In this model, each cylinder represents a fraction of the population, i.e., a group. Two contexts are considered: The dispersal can occur in a uniform habitat or in a fragmented habitat described by a conditional Boolean model. After the construction of the models, we investigate their properties: the first and second order moments, the probability that the population vanishes, and the distribution of the spatial extent of the population.     

A note on properties of spatial yule-walker estimators

For two-dimensional spatial autoregressive (AR) models, asymptotic properties of the spatial Yule-Walker (YW) estimators (Tjøstheim, 1978) are studied. These estimators although consistent, are shown to be asymptotically biased. Estimators from the first-order spatial bilateral AR model are looked at in more detail and the spatial YW estimators for this model are compared with the exact maximum likelihood estimators. Small sample properties of both estimators are also discussed briefly and some simulation results are presented.     

我国基础设施经济增长效应的传导机制实证检验

基础设施作用于交易效率进而促进经济增长的微观机制,能有效促进产出。文章采用空间计量经济学方法,对我国基础设施建设与经济增长的关系进行了实证分析,说明政府在基础设施建设中如果偏重于能大幅度提高交易效率的那些基础设施建设（比如公路、通讯等）,则会较大幅度地提高居民的福利水平。但是,当该比重达到一定水平后,交易效率和福利水平的提高就变得十分有限。这一结论是在提示政府：不能总是拿基础设施投入作为刺激经济增长的惟一手段,它不是拉动内需的灵丹妙药。     

Comparison of predictions by kriging and spatial autoregressive models

In geostatistics, the prediction of unknown quantities at given locations is commonly made by the kriging technique. In addition to the kriging technique for modeling regular lattice spatial data, the spatial autoregressive models can also be used. In this article, the spatial autoregressive model and the kriging technique are introduced. We extend prediction method proposed by Basu and Reinsel for SAR(2,1) model. Then, using a simulation study and real data, we compare prediction accuracy of the spatial autoregressive models with that of the kriging prediction. The results of simulation study show that predictions made by the autoregressive models are good competitor for the kriging method.     

随机效应广义空间滞后半参数变系数面板模型的估计

通过构建同时包含因变量和误差项空间滞后的随机效应半参数变系数面板模型,拓展了现有模型的灵活性和适应性。采用截面极大似然估计方法得出了参数和非参数的估计,理论证明发现：在一定的正则条件下,所有估计量具有一致性和渐近正态性。数值模拟显示：估计量具有良好的小样本性质,估计精度随着样本容量的增加而增加;空间权重矩阵的选择对估计量的表现没有产生显著差异,但是在Case权重矩阵下,当样本量相同时,空间相关系数的估计偏差随着空间权重结构复杂度的增加而扩大。     

真实固定效应空间随机前沿模型的贝叶斯估计

忽略个体效应和空间效应会严重干扰效率测算,其中忽略个体效应使得技术无效率项发生偏移,忽略空间相关性导致估计量有偏且不一致。本文基于真实固定效应随机前沿模型（引入了个体效应）,引入因变量和双边误差项的空间滞后项,构建了适用性更佳的真实固定效应空间随机前沿模型。对模型进行组内变化以消除额外参数,使用贝叶斯方法（需推导未知参数的后验分布并执行MCMC抽样）估计参数和技术效率。该方法真正克服了额外参数问题,比同类方法直观、简便。数值模拟结果表明,本文方法对参数、个体截距项及技术无效率项的估计精度均较高,且增加样本容量,估计精度变优。     

人口城市化空间路径的理论与研究及其启示

城市化的实践进程表明,一个国家的人口城市化往往遵循"城市化—郊区化—逆城市化—再城市化"或者"大城市—中等城市—小城市"的空间路径而展开。文章对"空间循环假说"、ROXY指数方法、"区域城市化"概念以及"差别城市化理论"等人口城市化空间路径理论的演绎进行了梳理,并对国内外相关研究进行了总结。结合中国人口城市化进程特点,文章认为,人口城市化空间路径理论与研究对中国城市化的道路模式、区域规划以及都市圈与城市群区域人口城市化问题的研究有启示作用。     

Extrapolative simulation of neighborhood networks based on population spatial distribution: Do they predict crime?

Objectives

Previous criminological scholarship has posited that network ties among neighborhood residents may impact crime rates, but has done little to consider the specific ways in which network structure may enhance or inhibit criminal activity. A lack of data on social ties has arguably led to this state of affairs. We propose to avoid this limitation by demonstrating a novel approach of extrapolatively simulating network ties and constructing structural network measures to assess their effect on neighborhood crime rates.

Methods

We first spatially locate the households of a city into their constituent blocks. Then, we employ spatial interaction functions based on prior empirical work and simulate a network of social ties among these residents. From this simulated network, we compute network statistics that more appropriately capture the notions of cohesion and information diffusion that underlie theories of networks and crime.

Results

We show that these network statistics are robust predictors of the levels of crime in five separate cities (above standard controls) at the very micro geographic level of blocks and block groups.

Conclusions

We conclude by considering extensions of the approach that account for homophily in the formation of network ties.     

SMPD Scenarios of Spatial Distribution of Human Population in China

Three scenarios of spatial distribution of human population in China are developed in the years 2010 and 2020, respectively by means of the method of surface modeling of population distribution (SMPD). Each one of the SMPD scenarios is defined as a plausible alternative future under particular assumptions of elevation, water system, net primary productivity (NPP), urbanization, transport infrastructure development, and population growth. The SMPD scenarios show that if population could freely migrate within the whole China, the balanced ratios of population in the western region, the middle region and the eastern region to total population in the whole China would be 16%, 33% and 52%, respectively.     

A working estimating equation for spatial count data

This paper proposes a working estimating equation which is computationally easy to use for spatial count data. The proposed estimating equation is a modification of quasi-likelihood estimating equations without the need of correctly specifying the covariance matrix. Under some regularity conditions, we show that the proposed estimator has consistency and asymptotic normality. A simulation comparison also indicates that the proposed method has competitive performance in dealing with over-dispersion data from a parameter-driven model.