WHY ARE URBAN TRAVEL TIMES SO STABLE?

Personal travel time in U.S. urban areas has been stable, clashing with the assertion that urban sprawl greatly lengthens travel. Average commute time rises by 7.7 percent with each cross‐sectional doubling of Metropolitan Statistical Area (MSA) jobs. Using the RELU‐TRAN structural computable general equilibrium model of the Chicago MSA, we simulate the equilibrium effects of a 24 percent population increase projected from 2000 to 2030 by the Chicago Metropolitan Agency for Planning. If no new road capacity is added, then congestion per mile increases. Although the urbanized land area increases by 19 percent, indicating sprawl, the vehicle miles traveled (VMT) per car‐trip decreases by 1.31 percent and the VMT per car‐trip to work decreases by 2.78 percent. Car travel time increases by only 6.25 percent and commuting time by only 4.54 percent, from 30.3 minutes in 2000 to 31.7 in 2030 or 3.4 seconds per year. We further explore the effects of new road capacity, gasoline prices, public transit speed, fuel economy gains, limits on suburban construction, and importantly, the cross‐elasticity of public transit use with respect to car times. The availability of public transportation, economizing on nonwork travel, and land use adjustments that increase job‐residence proximity keep times stable.     

Destination choices of Chinese rural–urban migrant workers: Jobs,amenities, and local spillovers

Using the 2014 China Migrants Dynamic Survey, we analyze rural–urban migrant workers’ destination choices after the global financial crisis, with an emphasis on jobs, amenities, and local spillovers. By using an equilibrium‐sorting model, this paper disentangles local spillovers from local attributes in the estimation process. We employ both an artificial instrumental variable and the provincial highway passenger flow in 1979 to tackle the endogeneity issue. After controlling for the network effects of migrants from the same origin, we find a separate and strong preference for colocating with a large population of migrants, regardless of origin. The results remain robust when we take into account labor supply‐driven migration, spatial autocorrelation between provinces, different industry definitions, and regional differences within provinces. Our results imply that due to institutional barriers, the rural‐migrant community will still be a very important factor in the foreseeable future. In addition, as the ongoing industrial upgrading and transfer policies in China may lead to a westward movement of rural–urban migrants, the movement will be expedited when the older, less educated, or lower income migrants relocate.     

The State of the Art in Modeling Migration in LDCS: A Comment

Early research on migration in LDCs, initially motivated by labor market postulates offered by Harris and Todaro, built upon general equilibrium models of interregional trade. In contrast, recent research on migration (such as Brueckner and Kim in this issue) builds upon a partial equilibrium analysis that is based on an urban land model. There are subtle differences between these models that complicate intermodel comparisons. The current paper, motivated by this complexity, has three purposes: (1) a mathematical explication of the state of the art in migration modeling, (2) a provision of further insights into the Todaro paradox, and (3) a suggestion for future research predicated on melding the urban land and interregional literatures.     

Front and Back Covers,Volume 34, Number 4. August 2018

Cover caption, volume 34 issue 4 Front Cover: INNOVATION IN A MEXICAN VILLAGE When Mexico's largest telecom companies refused to provide mobile phone service to the remote Zapotec mountain village of Talea de Castro, Oaxaca, residents responded with astonishing creativity: in March 2013, they built the world's first autonomous mobile phone network. The community‐owned network uses open‐source software to link mobile phones globally over the Internet using VoIP (Voice over Internet Protocol). It was developed in collaboration with a non‐profit organization, hackers and sympathetic activists committed to the idea of mobile access as a human right. Centuries‐old practices, including tequio (communal work party) and the asamblea (citizens' ‘assembly’ or town hall meeting), played a central role in enabling Zapotec citizens to give life to the network. Today residents of nearly 20 Zapotec, Mixtec and Mixe villages throughout Oaxaca can send and receive calls and texts within their communities for free, while long‐distance and international calls cost a small fraction of what commercial companies charge throughout the country. The network has provided villagers with an affordable and reliable system for maintaining family relationships and cultural continuity across national borders. However, Talea de Castro's community‐owned network is now under threat because Movistar, a giant telecom corporation based in Spain, has aggressively moved into the community. The case of Talea de Castro raises important questions about the roots of innovation, creative problem‐solving and the existential threats facing autonomous technological systems. Image source: DANIELA PARRA/REDES AC Back Cover: NORTH KOREA North Korean students against the backdrop of a statue of Kim Il‐sung (1912–1994) in Mansudae, central Pyongyang, 2007. Kim was the founding leader of North Korea and commanded the country's People's Army during the Korean War (1950–1953). For a decade after the war, his charismatic leadership contributed to turning the war‐torn society into a strong industrial economy. The importance of the last legacy is strongly propagated by the country's current leadership. In his guest editorial in this issue, Heonik Kwon considers the possibilities of a rapprochment between North Korea and the USA. Image source: (STEPHAN) / CC BY‐SA 2.0C     

河南省人口分布与乡镇可达性空间耦合特征

人口作为区域发展的内在因素,交通可达性提高将有利于促进人口或劳动力要素的自由流动和优化配置。在考虑土地利用及地形因素的基础上,采用包含乡村道的交通网络数据集,应用改进的成本距离计算方法,分析河南省乡镇可达性及其分布特征;通过乡镇可达性与人口密度的空间叠加,揭示人口分布与可达性的空间耦合特征。结果表明：①各乡镇可达性总体呈现明显的圈层分布,可达性值由内向外逐渐降低;时段越短,内部差异越大,交通指向越明显。②乡镇可达性与人口密度在各时间圈呈现正相关关系,可达性与人口分布集聚产生作用的最大时间距离为1.5h。③人口与交通可达性的空间耦合呈现较明显的半环状分布,社会经济指向性明显。④交通可达性对人口变化的影响具有时间阶段性和区域差异性。     

SEARCH FRICTIONS,UNEMPLOYMENT, AND HOUSING IN CITIES: THEORY AND POLICIES

We propose an urban search‐matching model with land development. Wages, unemployment, prices of housing and land are endogenously determined. We characterize the steady‐state equilibrium and then discuss the issue of efficiency. To explore interactions among markets, we implement comparative static analysis. We also consider three policies: an entry‐cost policy that reduces firms' entry, a transportation policy that reduces commuting costs, and a housing policy that decreases rental prices. We find that the transportation and housing policies are more efficient if the unemployment rate is low, while the entry‐cost policy is more efficient if the unemployment rate is high.     

ART‐P‐MAP Neural Networks Modeling of Land‐Use Change: Accounting for Spatial Heterogeneity and Uncertainty

Spatial land‐use models over large geographic areas and at fine spatial resolutions face the challenges of spatial heterogeneity, model predictability, data quality, and of the ensuing uncertainty. We propose an improved neural network model, ART‐Probability‐Map (ART‐P‐MAP), tailored to address these issues in the context of spatial modeling of land‐use change. First, it adaptively forms its own network structure to account for spatial heterogeneity. Second, it explicitly infers posterior probabilities of land conversion that facilitates the quantification of prediction uncertainty. Extensive calibration under various test settings is conducted on the proposed model to optimize its utility in seeking useful information within a spatially heterogeneous environment. The calibration strategy involves building a bagging ensemble for training and stratified sampling with varying category proportions for experimentation. Through a temporal validation approach, we examine models’ performance within a systematic assessment framework consisting of global metrics and cell‐level uncertainty measurement. Compared with two baselines, ART‐P‐MAP achieves consistently good and stable performance across experiments and exhibits superior capability to handle the spatial heterogeneity and uncertainty involved in the land‐use change problem. Finally, we conclude that, as a general probabilistic regression model, ART‐P‐MAP is applicable to a broad range of land‐use change modeling approaches, which deserves future research.     

Comparing closed system, flow-through and fluid infiltration geochemical modelling: examples from K-alteration in the Ernest Henry Fe-oxide–Cu–Au system

Potassic alteration of rocks adjacent to, and within the Ernest Henry Fe‐oxide–Cu–Au deposit is used here as a test case to investigate fluid–rock interactions using various equilibrium dynamic geochemical modelling approaches available in the HCh code. Reaction of a simple K–Fe–(Na,Ca) brine (constrained by published fluid inclusion analysis) with an albite‐bearing felsic volcanic rock, resulted in predicted assemblages defined by (i) K‐feldspar–muscovite–magnetite, (ii) biotite–K‐feldspar–magnetite, (iii) biotite–quartz–albite and (iv) albite–biotite–actinolite–pyroxene with increasing rock buffering (decreasing log w/r). Models for isothermal–isobaric conditions (450°C and 2500 bars) were compared with models run over a T–P gradient (450 to 200°C and 2500 to 500 bars). Three principal equilibrium dynamic simulation methods have been used: (i) static closed system, where individual steps are independent of all others, (ii) flow‐through and flush, where a part of the result is passed as input further along the flow line, and (iii) fluid infiltration models that simulate fluid moving through a rock column. Each type is best suited to a specific geological fluid–rock scenario, with increasing complexity, computation requirements and approximation to different parts of the natural system. Static closed system models can be used to quickly ascertain the broad alteration assemblages related to changes in the water/rock ratio, while flow‐through models are better suited to simulating outflow of reacted fluid into fresh rock. The fluid infiltration model can be used to simulate spatially controlled fluid metasomatism of rock, and we show that, given assumptions of porosity relationships and spatial dimensions, this model is a first‐order approximation to full reactive transport, without requiring significant computational time. This work presents an overview of the current state of equilibrium dynamic modelling technology using the HCh code with a view to applying these techniques to predictive modelling in exploration for mineral deposits. Application to the Ernest Henry Fe‐oxide–Cu–Au deposit demonstrates that isothermal fluid–rock reaction can account for some of the alteration zonation around the deposit.     

Land Reform in the Time of Neoliberalism: A Many‐Splendored Thing

Abstract: Over the past 20 years, land reform – defined here as the redistribution of land from large to small properties – has emerged as an important political issue in the Global South. Actors with widely differing ideological perspectives have claimed land reform as central to their political, social and economic platforms. In this paper, I compare reforms championed under the neoliberal auspices of the World Bank (the so‐called Market Led Agrarian Reforms) with those supported by popular grassroots actors such as the Movement of Landless Workers (the MST) in Brazil. I argue that although these two approaches to land reform are often considered antithetical to one another, they share a common theoretical foundation. Both are rooted in a labor theory of property that attributes the fruits of one's labor to the laborer. Where the two differ is in their interpretation of the “original sin” through which land and labor came to be misaligned: neoliberal actors see the state as the key source of land‐related inefficiency while popular grassroots actors identify the market as the key source. I analyze case material from northeastern Brazil and suggest that the institutionalization of the labor theory of property (across civil society, state and market in the region) has generated insecurities for new land reform beneficiaries who must protect their property rights with visible evidence of their productivity.     

DIGGING PITS AND MAKING PLACES AT UĞURLU DURING THE SIXTH MILLENNIUM BC

The site of U?urlu on the island of Gökçeada (Imbros) is the earliest known Neolithic settlement within the Aegean Islands (c.6800–4500 cal. BC). In total, 37 pits, associated with a rich variety of artefacts as well as human and animal bones were excavated in the Late Neolithic and Early Chalcolithic levels of the site (c.5900–4500 BC). The pits belonging to the early sixth millennium BC levels of U?urlu were small and located within the houses that seem to have gone through multiple episodes of house destruction and renovation rituals. During the late sixth millennium BC, this area became the focus of extensive pit‐digging activity, when large pits involving rich variety of artefacts were set within the courtyard of a special building (Building 4). Among the pits, a collective human burial pit (P188) incorporating the remains of 11 individuals and another pit (P52) involving a partial human skeleton were also found. From a comparative point of view, the construction techniques of these pits, their spatio‐temporal relations as well as their associated archaeological artefacts resemble the Anatolian and Near Eastern Neolithic practices of house destruction and renovation cycles, which are activities related to the ancestor cults of the region. We argue that all of these practices reflect public events during which social relations were negotiated through the agency of place. The differences observed during the sixth millennium BC at U?urlu reflect the changing concepts of place and society in the immediate aftermath of the Neolithic Process, when interactions with the Balkans as well as the Aegean intensified in this region.     

LOCAL FOOD,URBANIZATION, AND TRANSPORT‐RELATED GREENHOUSE GAS EMISSIONS

We argue that “buying local” does not necessarily reduce transport‐related greenhouse gas emissions, even if production technologies and yields are homogeneous in space. We develop a partial‐equilibrium model of rural‐urban systems where the spatial distribution of food production within and between regions is endogenous. We exhibit cases where locating some food production in the least‐urbanized regions results in lower emissions and higher welfare than if all regions are self‐sufficient. The optimal spatial allocation of food production does not exclude the possibility that some regions should be self‐sufficient, provided that their urban population sizes are neither too large nor too small.     

Modeling Air Quality in Urban Areas: A Cell‐Based Statistical Approach

Statistical regression models are presented that explain the observed variations, across urban areas, in the concentrations of two major pollutants, ozone and carbon monoxide. Model specification and estimation are based on an explicit and new spatial framework derived from the theoretical concept of well‐mixed cells, whereby the basic Fickian system of diffusion equations is integrated over the regional space partitioned into a grid of large cells. The concentration in each cell results from the balance of pollutant flows into and out of this cell and of pollutant emissions and removal within that cell, and is expressed as the sum of two concentration contributions: (1) the local effect, dependent upon pollution‐related factors around the measuring station, and (2) the regional effect, dependent upon pollutant flows originating outside the local area. A large database is developed, making extensive use of GIS technology, to spatially relate such data as pollution measurements, meteorological factors, land‐use characteristics, census socioeconomic data, and major highway network characteristics. The results confirm the appropriateness of the well‐mixed cell framework, are in line with general knowledge regarding the determinants of ozone and carbon monoxide concentrations, and clarify the role of transportation, residential fuel use, economic activities, natural environments, and meteorological factors such as temperature and solar radiation. About SO percent of the variations in concentrations are explained by these models. Several areas of further research are outlined.     

Inferring intermediate‐scale fluid flow in a heterogeneous metasedimentary multilayer sequence during progressive deformation: evidence from the Monts d’Arrée slate belt (Brittany,France)

Quartz veins in the early Variscan Monts d’Arrée slate belt (Central Armorican Terrane, Western France), have been used to determine fluid‐flow characteristics. A combination of a detailed structural analysis, fluid inclusion microthermometry and stable isotope analyses provides insights in the scale of fluid flow and the water–rock interactions. This research suggests that fluids were expelled during progressive deformation and underwent an evolution in fluid chemistry because of changing redox conditions. Seven quartz‐vein generations were identified in the metasedimentary multilayer sequence of the Upper Silurian to Lower Devonian Plougastel Formation, and placed within the time frame of the deformation history. Fluid inclusion data of primary inclusions in syn‐ to post‐tectonic vein generations indicate a gradual increase in methane content of the aqueous–gaseous H₂O–CO₂–NaCl–CH₄–N₂ fluid during similar P–T conditions (350–400°C and 2–3.5 kbar). The heterogeneous centimetre‐ to metre‐scale multilayer sequence of quartzites and phyllites has a range of oxygen‐isotope values (8.0–14.1‰ Vienna Standard Mean Ocean Water), which is comparable with the range in the crosscutting quartz veins (10.5–14.7‰ V‐SMOW). Significant differences between oxygen‐isotope values of veins and adjacent host rock (Δ = ?2.8‰ to +4.9‰ V‐SMOW) suggest an absence of host‐rock buffering on a centimetre scale, but based on the similar range of isotope values in the Plougastel Formation, an intraformational buffering and an intermediate‐scale fluid‐flow system could be inferred. The abundance of veins, their well‐distributed and isolated occurrence, and their direct relationship with the progressive deformation suggests that the intermediate‐scale fluid‐flow system primarily occurred in a dynamically generated network of temporarily open fractures.     

Isotopic and petrological evidence of fluid–rock interaction at a Tethyan ocean–continent transition in the Alps: implications for tectonic processes and carbon transfer during early ocean formation

We report overprinting stable isotope evidence of fluid–rock interaction below two detachment faults along which mantle rocks were exhumed to the seafloor, between the respective landward and seaward limits of oceanic and continental crust, at a Tethyan ocean–continent transition (OCT). This OCT, which is presently exposed in the Tasna nappe (south‐eastern Switzerland) is considered an on‐land analogue of the well‐studied Iberian OCT. We compare our results with the fault architecture (fault core–damage zone–protolith) described by Caine et al. [Geology (1996) Vol. 24, pp. 1025–1028]. We confirm the existence of a sharp boundary between the fault core and damage zone based on isotopic data, but the boundary between the damage zone and protolith is gradational. We identify evidence for: (1) pervasive isotopic modification to 8.4 ± 0.1‰ which accompanied or post‐dated serpentinization of these mantle rocks at an estimated temperature of 67–109°C, (2) either (i) partial isolation of some highly strained regions [fault core(s) and mylonite] from this pervasive isotopic modification, because of permeability reduction (Caine et al.) or (ii) subsequent isotopic modification caused by structurally channelled flow of warm fluids within these highly strained regions, because of permeability enhancement, and (3) isotopic modification, which is associated with extensive calcification at T = 54–100°C, primarily beneath the younger of the two detachment faults and post‐dating initial serpentinization. By comparing the volumetric extent of calcification with an experimentally verified model for calcite precipitation in veins, we conclude that calcification could have occurred in response to seawater infiltration, with a calculated flux rate of 0.1–0.2 m year^?1 and a minimum duration of 0.2–4.0 × 10⁴ years. The associated time‐averaged uptake flux of carbon during this period was 8–120 mol m^?2 year^?1. By comparison with the estimated area of exhumed mantle rocks at the Iberian OCT, we calculate a maximum annual uptake flux for carbon of 2–30 Tg year^?1. This is an order of magnitude greater than that for carbon exchange at the mid‐ocean ridges and 0.1–1.4% of the global oceanic uptake flux for carbon.     

NEW DIRECTIONS FOR URBAN ECONOMIC MODELS OF LAND USE CHANGE: INCORPORATING SPATIAL DYNAMICS AND HETEROGENEITY*

ABSTRACT We review the usefulness of urban spatial economic models of land use change for the study and policy analysis of spatial land use–environment interactions. We find that meaningful progress has been made in econometric and monocentric models extended to account for multiple sources of spatial heterogeneity and in the development of general equilibrium models with spatial dynamics. Despite these advances, more work is needed in developing models with greater realism. Most agent‐based computational models of urban land use change currently lack economic fundamentals, but provide a flexible means of linking microlevel behavior and interactions with macrolevel land use dynamics. In combination with empirical methods to identify parameters, this framework provides a promising approach to modeling spatial land use dynamics and policy effects.     

In Loving Memory of Mary Belshaw,May McRidge,and the Nyungar People of the Badjaling Mission, 1930–1954

Using examples from his family and religious history, Patrick O’Farrell analysed the transition from Irish emigrant to assimilated colonial in what was perceived as vacant land. Like O’Farrell, this article will also use family history to address the issues of memory, religion, and assimilation. The Irish weaver Mary Belshaw (1879–1960) came to Australia in 1913 and was instrumental in the emigration of her family to Australia during the 1920s. She worked as a Protestant missionary among Aboriginal Australians from 1915, until her retirement in 1953. Although the grave she shares with her co‐worker May McRidge (1882–1943) bears the words “Ever remembered by what she has done,” her story was largely forgotten by her family. In 1986, the Nyungar people erected a memorial stone to Belshaw and McRidge and the thirty‐nine Nyungar families who lived at the Badjaling Mission in Western Australia from 1930 to 1954. This article will address the wider issues in twentieth‐century Australia which contributed to the neglect of the story by Belshaw's Irish Australian family and then led to its recovery. It will reveal how an Irish heritage was rediscovered because the story lived within a Nyungar community who had survived terra nullius and assimilation policies to return to their land at Badjaling.     

Climate Aridity and Land Use Changes: A Regional‐Scale Analysis

In recent years, aridity and drought have become crucial issues at the global scale because of their environmental and socio‐economic implications. On the one hand, aridity causes a reduction in the biological and economic productivity of terrestrial ecosystems, and represents a serious threat to ecological, biogeochemical, and hydrological processes. On the other hand, human use (and abuse) of vulnerable dry land ecosystems may lead to unsustainable land management. Based on these considerations, this paper analyses the recent land cover changes observed in Latium (Italy) during the exceptionally dry period 2000–2007. More than 50% of the area investigated was classified as dry in 2004–2007 compared with 0% in 2000–2003. Moreover, climatic aridity impacted differently on semi‐natural, agricultural, and built‐up land. These findings illustrate a possible scenario for suburban Mediterranean regions: increasing aridity (mainly due to rising temperatures) mainly impacting on peri‐urban land.     

Monitoring Land‐Cover and Land‐Use Change in a Rapidly Urbanising Coastal Environment: the Maroochy and Mooloolah Rivers Catchments,Southeast Queensland, 1988–1997

Effective catchment monitoring requires an integrative approach for selecting remotely sensed data to monitor land‐cover change. Catchment analyses and monitoring requirements in the Maroochy and Mooloolah River Catchments (south‐east Queensland) were addressed by linking government and community information needs to appropriate scales of remotely sensed data and processing routines. A hybrid image classification approach applied to Landsat Thematic Mapper image data acquired in 1988 and 1997 provided catchment scale land‐cover maps (with accuracies of 73% and 84%). Land‐cover change maps derived from post‐classification comparison provided information on the spatial distribution and type of land‐cover changes between 1988–1997. Land‐cover change was dominated by activities related to urban residential expansion (suburban and rural residential) and agricultural expansion (sugar cane farms). Significant spatial variations in the geometric registration accuracy of the image data sets and classification accuracies produced moderate to low change detection accuracies. However, the framework and community consultation used for selecting and processing data ensured the resource managers and community groups were fully aware of the limitations of the land‐cover change mapping process and that the output images were suitable for incorporating in resource monitoring activities.     

LOCAL INPUT AND PRODUCTIVITY GROWTH IN U.S. MANUFACTURING: 1972–2002*

ABSTRACT This research analyzes manufacturing growth and decline across metropolitan and nonmetropolitan regions during the 1972–2002 period. We decompose real value added growth across local labor market areas in the lower 48 U.S. states into contributions from labor, capital, and total factor productivity. We then estimate a model describing the long‐run growth of labor, capital, and productivity and find that increased productivity increases the growth of labor and capital, as well as a positive correlation between labor and capital stock growth. We also find evidence that human capital investment and agglomeration economies encourage productivity growth, while unionization discourages it.     

Employment Opportunities,Wages and International Migration in Sweden 1970–1989

In this study I focus on the impact of aggregate labor turnover and regional labor market conditions on gross in- and out-migration within the framework of a neoclassical flexible-wage (equilibrium) model and a fixed-wage (labor-market disequilibrium) model. Using annual panel data on internal gross migration flows in Sweden from 1970 to 1989, I find that regional differences in employment opportunities have the expected effects on migration. The empirical relationship between real wages and gross migration flows is found to be less congruent with theory implications, indicating that compensated regional income prospects are equalized primarily via the interaction between employment opportunities and gross migration flows. Cyclical changes in hirings are shown to have a robust and strongly significant positive scale effect on migration.