城市“规模”偏小不利于经济增长吗?——两种借用规模视角下的再审视

城市规模偏小是否就一定不利于其经济增长,推进大城市建设是否就一定能实现区域经济发展的可持续?关于此问题的争论从未间断,而相关的经验证据还有待进一步加强。基于2003—2016年我国283个地级市面板数据,采用面板双固定效应模型、空间计量模型、系统GMM模型以及面板门限模型等方法,在开放型城市系统模型的假设下,本文拟从绩效规模借用和功能规模借用的视角来再审视城市经济活动密度、人口规模与经济增长的关系,以此来破解中小城市高速增长难题。本文研究发现:①绩效规模借用能帮助中小城市实现超越其自身经济活动密度所能达到的集聚经济水平;而功能规模借用则能通过帮助中小城市实现更高等级职能专业化水平的方式,促进其经济快速增长。②此外,通达性水平的提升能同时强化这两种借用规模的作用效果。③最后,就借用规模的异质性表现来看,在城市群内部,中小城市以借用规模行为占主导,而大城市则以发挥集聚阴影作用为主。基于以上结论,本文主要政策建议如下:①政府在制定区域发展规划和交通网络规划时应该以城市群经济建设为目标,努力消除大中小城市的行政壁垒,实现大中小城市的共赢式发展。②城市群经济的建设可以以大城市为中心展开,同时以能充分发挥中小城市借用规模的思路来发展。     

北京市人口动态模拟与政策分析

随着城市化进程的加快,我国城市规模不断膨胀,超过1 000万的超大城市不断涌现,城市人口规模过大、增长过快以及带来的城市问题引起社会各界的关注。北京作为一个人口超过2 000万的超大城市,不仅具有超大城市的一般特征,而且具有首都所在城市的特点。本文在厘清北京人口增长机制的基础上,采用系统动力学方法,通过政策模拟,考察不同政策导向对未来北京市人口增长趋势的影响,得到以下结论:1如果保持当前的经济增长速度,并按当前的生产技术水平以及产业结构变化趋势发展,未来北京人口规模将持续快速增长,到2030年将突破3 000万人,2050年将接近5 000万人,城市面临巨大的人口压力。2单纯通过产业结构升级对调控人口作用有限。3适当放缓经济增长速度以及大力提高劳动生产率可以有效控制人口的快速增长,挤出大量的低端劳动力,人口调控效果明显。4户籍制度的适度放开在一定程度上减少了外来人口规模,但对人口总量的减少并没有起到作用。5与单纯采用一种政策调整相比,多种调控政策并举调控人口的效果更佳。由此得到以下几点启示:首先,每个城市都应该有自己的功能定位,决不能搞"大而全"和千城一面,尤其不能将城市经济增长速度和总量作为城市发展的主要目标甚至唯一目标,不顾后果和不择手段地追求GDP。否则城市人口规模的无序扩大就很难避免,也很难治理。对于北京而言,发挥其政治、文化、国际交往以及科技创新中心的首都功能,大力发展现代服务业,提高劳动生产率,优化产业结构才有利于人口的有序发展。另外,政府在人口调控方面必须有所作为,但也不能对人口调控进行大包大揽,取代市场。政府要顺应经济和社会发展的规律,顺势而为,出台相应的系列综合性调控政策。只有这样,才能对人口调控起到更好的效果。     

对中国不同区域大中小城市真实收入的比较

城市规模与城市真实人均收入水平呈"倒U"关系,"倒U"曲线的顶点对应的才是最优城市规模和最大真实人均收入水平。本文通过对我国东中西部大中小城市经生活成本调整后的真实收入水平比较后发现,一方面,东部大型城市的真实收入水平已经低于部分东部中小城市和中西部核心城市;另一方面,仍存在许多内陆中小城市的真实收入水平低于东部大型城市,这将会成为吸引人口继续流入大城市的重要因素,未来大型城市仍将面临较大的人口压力。     

基于集聚经济规律的城市规模问题研究

本文分析了2000年-2010年中国城市规模的变化规律,借鉴集聚经济理论对上述变化规律给出合理解释,并指出以不同产业为主的城市之间的适度规模差异巨大。首先,使用第五次人口普查、第六次人口普查中全国地级市的城镇地区人口数据,文章首次计算并比较了2000年和2010年中国城市的规模位序。结果发现总体上我国的城镇体系发展较为平衡、首位度低,10年间中国城市体系中人口往大城市集中的特征明显,高位次城市发展突出;但是在规模前100位的城市中,人口分布则更为平衡。这表明10年间中国一批大城市发展迅速,人口分布存在着明显的"集中与扩散并存"的趋势。进一步地,基于集聚经济理论,文章构造了城市单位生产成本函数,指出城市的单位生产成本伴随着城市规模的扩大呈现出"U"型曲线特征,城市规模不能无限制的扩大。本文将城市的适度规模界定为城市单位生产成本最小时所对应的规模,利用中国地级市的面板数据,采用异方差稳健性估计的固定效应模型,测度了中国城市的适度规模。测算结果表明,在其他条件不变的情况下,城市的适度规模为420万人。这一结果也同时证实了目前中国的城市规模是普遍偏小的,人口往大城市迅速集中可以降低城市的生产成本,当前城市体系的发展趋势符合经济理性。此外,文章认为,现实中各个城市之间的产业结构差别巨大,这使得上述对城市适度规模的估计只是一个"一般情况"下的估计。一个城市的适度规模部分地取决于这个城市的产业特征。一个城市中追求集聚效益的产业越多,那么这个城市的适度规模就会越大。在界定制造业集聚型城市和生产性服务业集聚型城市的基础上,文章的实证结果进一步表明,与"一般情况"下的城市适度规模相比,制造业集聚型城市的适度规模较小,生产性服务业集聚型城市的适度规模更大。     

极化与扩散:长三角在区域均衡发展中的作用——来自长三角与长江中游城市群的证据

从长三角一体化视角出发,使用Dagum基尼系数分解,经济增长的空间外部性理论模型,空间滞后计量模型(SAR)等方法考察了长三角与长江中游两大城市群均衡发展的演化趋势,分析了长三角城市群的极化-扩散效应对长江中游城市群经济增长以及区域均衡发展的促进作用.研究表明:(1)长三角的一体化进程并未扩大其与长江中游的发展水平差距,事实上,两大城市群“组间差异”的缩小是区域均衡发展的主要推动力,而“组内差异”缩小的影响则相对微弱.(2)长三角城市群对长江中游城市群的扩散效应大于极化效应,即长三角通过正向的空间溢出效应促进了长江中游经济发展,缩小了两地的发展水平差距,但如果忽略长江中游内部的空间相关性则会明显高估长三角的扩散效应.(3)长江中游内部的均衡发展水平越高,越有助于长三角扩散效应的充分发挥.(4)长三角不同城市的扩散效应受经济规模、产业结构等因素与地理距离的交互作用,呈现出非线性模式.     

人口集聚对创业活跃度的影响:考虑集聚动态的效应与路径北大核心CSCDCSSCI

文章基于创业资源与创业情景理论,结合人口集聚的规模效应和外部效应,并充分考虑人口集聚具有动态性的特征,构建了人口集聚影响创业资源获取、创业机会需求以及创业环境保障的理论分析框架。在此框架下使用2008—2019年中国224个地级市市辖区的平衡面板数据,引入历史建成区面积作为人口集聚的工具变量,实证检验了人口集聚影响创业活跃度的直接效应与间接路径。结果表明:①人口集聚可以显著促进城市创业活跃度提升,控制人口集聚的内生性问题会避免低估人口集聚对创业活跃度的促进作用。②人口集聚对创业活跃度的促进作用有显著的滞后效应,且滞后效应的有效时间边界为滞后三期。③人口集聚通过扩大城市市场需求和带动城市基础设施建设提升创业活跃度的部分中介效应显著。按照城市规模等级分组进行拓展性分析显示:④超大城市和特大城市的人口集聚对创业活跃度既没有显著的促进作用也没有显著的挤出效应。⑤大城市和中小城市的人口集聚对城市创业活跃度有显著的促进作用,但对人口集聚指标分解发现中小城市的就业人口和建成区面积增量已经停滞不前甚至减少。基于以上结果,文章建议:①探索将创业支持政策作为基本公共服务,面向常住人口实现全覆盖。②继续引导人口向各级城市集聚,人口在城市中集聚有助于做大国内市场。③城市基础设施的规划和建设要与人口集聚的速度和规模相适应,应当考虑适度超前于人口集聚的速度。     

安徽省城市体系等级规模结构特征及其调整

等级规模结构是城市体系的三大结构之一,其特征可以反映出城市在不同规模级中的分布状况及城市人口集中或分散的程度,有助于认识城市体系发展所处的阶段。运用统计数据,在深入分析的基础上,发现安徽省现状城市体系的等级规模结构呈位序—规模分布;城市首位度偏低,规模效应不明显;城市规模总体偏小,特大城市和大城市发育不足,中等城市突出;城市规模空间分布不均衡,区域分异明显。在安徽省城市体系动态变化过程中,等级规模结构相对稳定但不断趋于集中,首位城市发展潜力较大,同时各规模级城市具有不同的变化趋势和特征。在此基础上提出了加快皖江城市带的建设、促进皖北城市群的发展、提高皖南中等城市和中心镇水平等优化建议。     

土地价格上涨如何改善城市土地利用效率?北大核心CSCDCSSCI

面对城市土地资源稀缺加剧的现状,该研究将探讨依靠价格手段倒逼城市土地利用效率改善的路径及作用方向。文章采用2007—2019年280个地级市的面板数据,运用动态空间杜宾模型,从总体和分用途规模两大层面系统刻画土地价格上涨对于城市土地利用效率改善的短期和长期效应,考察同等规模城市的地方政府在面对价格变动时所产生的策略互动。研究结果表明,总体层面:城市土地价格的升高改善了本地区城市土地利用效率,但对周边地区的效率却产生了抑制作用。分用途-规模层面:①商住用地价格的升高在短期内促进了效率的改善,在长期内的影响逐渐减弱。此外,短期内政府间的策略互动主要体现为“虹吸吸应”。长期来看,同等规模的大城市之间主要体现为“示范效应”,中小城市之间则主要体现为“虹吸效应”。②工业用地价格在短期内对于效率的改善并不显著,而在长期则起到了较为明显的推动作用。短期内政府间的策略互动主要体现为“虹吸效应”。长期来看,同等规模的大城市之间主要体现的是“示范效应”,中小城市之间则体现为“虹吸效应”。因此,对于商住用地而言,应继续深化“招拍挂”出让制度以及财税制度改革,避免唯“价高者得”。对于工业用地而言,应将有效的市场化出让机制与有为的政府管理相结合,建立起上中下游精细化、多层次的协同管理体系,确保土地利用效率的长期改善。     

产业发展对城市蔓延影响的差异性分析——以长江经济带104个城市为例

经济由高速增长向高质量转变的背景下,土地城市化快于人口城市化而带来的城市蔓延不利于城市的高质量可持续发展。基于2001~2015年长江经济带面板数据考察了产业发展对城市蔓延的差异性影响，研究发现：（1）总体上，在产业结构方面，随着第二产业就业比重的增加，城市蔓延度提高。而随着第三产业就业比重增加时，城市蔓延减缓，这其中起主要作用的是生活性服务业。（2）从城市规模角度来看，第二产业对城市蔓延的影响，在中小城市起显著的作用，而在大城市不显著。第三产业在大城市起显著的抑制性作用，而在中小城市不显著，这主要与不同城市规模下集聚经济效益的发挥有关。（3）从蔓延类型角度来看，推动城市蔓延向集约型方向发展的主要是第三产业中的生活性服务业，而第二产业以及生产性服务业推动城市蔓延向过度蔓延方向发展。长江经济带应合理布局第二产业，大力发展第三产业，提高产业的集聚效应,同时避免不合理开发和盲目招商引资而造成的城市蔓延。     

“十三五”中国城镇化六大转型与健康发展

新型城镇化是中国最大的潜在内需,是深化供给侧结构性改革的突破口,是引领"十三五"时期经济发展的引擎。本文在对中国城镇化深入分析的基础上,发现当前中国城镇化面临着以人为本不够、城镇化效率不高、绿色发展不够、城镇规模结构不平衡、市场化不足、协调发展不够六大问题。结合"十三五"规划纲要提出的"创新、协调、绿色、开放、共享"的新发展理念,文章认为"十三五"期间城镇化要实现健康发展,需要推动六大转型:(1)通过采取差别化落户政策和居住证制度并行的市民化二维路径,实现从以地为中心的城镇化转向以人为本的城镇化;(2)通过土地价格市场化、提升人力资本、避免重复投资和过度投资来提高土地、劳动、资本的使用效率,实现从低效利用要素的城镇化转向高效率和高质量的城镇化;(3)通过转变经济发展方式和提升城市管理水平,实现从"高耗能、高排放、高污染"的城镇化转向人口、资源、环境可持续发展的绿色城镇化;(4)通过依托城市群这一平台,实现从规模结构不合理、大中小城市不协调的城镇化转向城市群一体化高效发展、大中小城市协调发展、规模效应和集聚效应充分发挥的城镇化;(5)通过转变政府职能,发挥市场机制在资源配置中的决定性作用,实现从"政府主导"的城镇化转向"市场主导、政府引导"、民间资本作用充分发挥的城镇化;(6)通过推动信息化和工业化深度融合、工业化和城镇化良性互动、城镇化和农业现代化相互协调,实现从城镇化与工业化、信息化、农业现代化发展不协调、产城脱节转向"四化同步"、产城融合的发展方式。     

WSSD 2002, Latin America and Brazil: Biodiversity and Indigenous People

Latin America comprehends notable variations in terms of natural environment, availability of natural resources, living standards, and demographic patterns. Latin America is a mosaic of cultures, post- and pre-Columbian. The rich variety of life forms discovered and described by chroniclers and traveling naturalists in the Neotropics contributed to the proposal, in mid-XVIIIth century, of a new system of classification and a scientific code of nomenclature for all organisms. Biodiversity was, for many centuries, a source of resources to be exploited in natura. In scientific circles, its inventory became the domain of taxonomists. But modern technology showed how important the miriad of life forms really are as sources of chemical molecules to be engineered as drugs and reassembled as novel manufactured products. We are on the brink of a new agricultural and medical revolution, thanks to the techniques of genetic engineering, which will lead eventually to the elimination of hunger and malnutrition.In this essay, the Brazilian environmental and social heterogeneity will serve as an example to illustrate some key points, which have influenced sustainability policies. The Amazon deforestation and indigenous knowledge (IK), subjects often associated with areas of high biodiversity, are usually the focus of environmental debates. The importance of IK in integrating development, reducing poverty and sustainability are considered together with the intellectual property rights of native populations.In the World Summit on Sustainable Development (WSSD) Implementation Plan, a few paragraphs were dedicated to Latin America, because of the pre-existing Action Platform on the Road to Johannesburg 2002, approved in Rio de Janeiro in October 2001. This paper calls attention to the need to draw up specific environmental policies for a region which shows an extremely high cultural and biological diversity, associated with a high availability of forests and water, among other resources.     

Household water in rural asia: a case study of the construction of a piped water system in Bangui,Ilocos Norte,Philippines

In early 1980 an extension agent was assigned to the rural municipality of Bangui, Ilocos Norte, Philippines to work on development projects – in particular the improvement of the supply of safe water for drinking and sanitation. After many months of visiting spring sites and meeting with community leaders, a small part of the municipality was selected to build a gravity fed piped water system. Although the system took many months to plan, identify funding and construct, the 600 community members were ultimately rewarded with house to house connections that enabled them to achieve per capita water consumption levels above the minimum levels recommended by the World Health Organization. Of course, money was critical to ensure the project’s success, but many other factors played an equally critical role. For instance, without the active participation of the community and the unwavering support of the community leadership the project would not have survived the initial planning stage. Also, the extension agent played a critical role by acting as a conduit between funding agencies, the Bureau of Public Works and the community. The primary lesson to be learned from this experience is that the success of rural development projects is largely driven by the synergy between the community, technical support, financial support, and agents of change such as extension agents. If any of these ingredients had been lacking, the project result would likely have been far different.     

Human exposure to polybrominated diphenyl ethers (PBDE), as evidenced by data from a duplicate diet study, indoor air, house dust, and biomonitoring in Germany

Polybrominated diphenyl ethers (PBDE) are used as flame retardants in a wide variety of products. As part of the Integrated Exposure Assessment Survey (INES), this study aimed to characterize the exposure of an adult German population using duplicate diet samples, which were collected daily over seven consecutive days, and indoor air and house dust measurements. Our study population consisted of 27 female and 23 male healthy subjects, aged 14–60 years, all of whom resided in 34 homes in southern Bavaria. In these 34 residences the air was sampled using glass fiber filters and polyurethane foams and the dust was collected from used vacuum cleaner bags.The median (95th percentile) daily dietary intake of six Tetra- to HeptaBDE congeners was 1.2 ng/kg b.w. (3.3 ng/kg b.w.) or 67.8 ng/day (208 ng/day) (calculated from the 7-day median values of each study subject). Concentrations in indoor air and dust (cumulative Tri- to DecaBDE congener readings) ranged from 8.2 to 477 pg/m³ (median: 37.8 pg/m³) and 36.6 to 1580 ng/g (median: 386 ng/g), respectively. For some congeners, we identified a significant correlation between air and dust levels.The median (95th percentile) blood concentration of total Tetra- to HexaBDE congener readings was 5.6 (13.2) ng/g lipid. No significant sex differences were observed, but higher blood concentrations were found in younger participants. Using a simplified toxicokinetic model to predict the body burden from exposure doses led to results that were of the same order of magnitude as the measured blood concentrations.Based on these measurements and given our exposure assumptions, we estimated for the total tetra- to heptabrominated congener count an average (high) comprehensive total daily intake of 1.2 ng/kg b.w. (2.5 ng/kg b.w.). Overall, our results suggest that dietary exposure is the dominant intake pathway at least in our study population, responsible for 97% (average intake) and 95% (high intake) of the total intake of an adult population.     

A new general mechanistic river model for radionuclides from single pulse fallouts which can be run by readily accessible driving variables

This paper presents a new general, process-based river model for substances such as radionuclides from single pulse fallouts. The new model has been critically tested using data from 13 European rivers contaminated by radiocesium from the Chernobyl accident. This modelling approach gives radionuclide concentrations in water (total, dissolved and particulate phases; and also concentrations in sediments and fish, but the latter aspects are not discussed in this paper) at defined river sites. The model is based on processes in the upstream river stretch and in the upstream catchment area. The catchment area is differentiated into inflow ( approximately dry land) areas and outflow ( approximately wetland) areas. The model also accounts for time-dependent fixation of substances in the catchment. The catchment area sub-model is based on a previous catchment model, which has been tested with very good results for radiocesium, radiostrontium and Ca-concentrations (from liming operations). The new river model is simple to apply in practice since all driving variables may be readily accessed from maps and standard monitoring programs. The driving variables are: latitude, altitude, continentality, catchment area, mean annual precipitation, soil type (percentages or organic and sandy soils), fallout and month of fallout. Modelled values have been compared to independent empirical data from 10 rivers sites (91 data on radiocesium in water) covering a wide domain (catchment areas from 4000 to 180 000 km(2), precipitation from 500 to 960 mm/yr and fallout from 1700 to 660 000 Bq/m(2)). The new model predicts very well--when modelled values are compared to empirical data, the slope is perfect (1.0) and the r(2)-value is 0.90. This is good giving the fact that there are also uncertainties in the empirical data, which set a limit to the achieved predictive power, as expressed by the r(2)-value.     

The influence of hot particle contamination on Sr and Cs transfers to milk and on time-integrated ingestion doses

Most models for transfers of radionuclides through the food chain typically assume that the radioactivity is initially deposited in chemically available forms. It is known, however, that releases of radionuclides in the form of hot particles may significantly influence their environmental transfers and uptake to the food chain. This study presents models for time changes in ⁹⁰Sr and ¹³⁷Cs in milk which incorporate hot particle contamination using observed rates of hot particle dissolution following the Chernobyl accident. A general equation is presented for the influence of hot particles on overall ingestion doses. As expected from previous work, fallout of hot particles significantly influences time changes in radionuclide activity concentrations in foodstuffs. It is also shown that incorporation of radionuclides in hot particles influences time-integrated ingestion doses. For a situation in which a large proportion (90–100%) of fallout is in slowly dissolving hot particles, time-integrated ingestion doses from ⁹⁰Sr and ¹³⁷Cs are reduced by a factor of approximately two compared to the case where all radioactivity is deposited in bioavailable forms. However, the influence of rapidly dissolving hot particles on time-integrated ingestion doses is relatively minor. Remaining significant uncertainties in dose estimates are discussed.     

Narratives,Rhetorical Genres,and Environmental Conflict: Responses to Schwarze's “Environmental Melodrama”

The appearance of Steven Schwarze's essay, “Environmental Melodrama” (Schwarze, 2006) as the lead article in a recent issue of The Quarterly Journal of Speech marks an important moment of recognition for environmental communication scholarship. Schwarze's essay demonstrates how studies of environmental rhetoric can contribute to rhetorical theory more generally, while addressing practical questions regarding the rhetorical aspects of environmental conflict. The contributors to this forum respond to Schwarze's arguments, drawing in part upon their own case studies of rhetorical action and narrative in environmental conflict.     

The Phenomenon of Pseudoviviparity in Alpine and Arctomontane Grasses (DeschampsiaBeauv., FestucaL., and PoaL.)

It is known that pseudoviviparous plant taxa are most numerous in the Arctic and high mountain regions, where they sometimes account for a noticeable part of the local flora and play an important phytocenotic role. The complex of pseudoviviparous taxa is an interesting model for investigating the processes of hybridogenic speciation, as various mechanisms stabilizing the hybrid genetic systems proved to be effective in them. In particular, this concerns vast and taxonomically complex groups such as the genera Deschampsia, Festuca, and Poa.In this paper, published data on the taxonomy, chromosome numbers, and distribution of pseudoviviparous grasses in the Arctic regions and subarctic mountain systems are reviewed.     

Communities of hydrobionts developing at the water-rock interface in Lake Baikal

Development of benthic communities on rocks from the interdisciplinary test site near Cape Berezovyi (southern Baikal) is analyzed. Rock plates were placed on the bottom in the shallow-water zone of Baikal for six months, and a community consisting of microorganisms, microphytobenthos, and meiobenthos developed on them. The development and activity of hydrobionts depended on the chemical composition and structure of the rock. Marble and granite plates were populated by them more selectively than amphibolite plates. It is supposed that the biota plays an important role in destruction of rocks in the shallow-water zone of Baikal.