Matchmaking in nairobi the role of land use

Well-functioning cities reduce the economic distance between people and economic opportunities. Cities thrive because they enable matchmaking -- among people, among firms, and between people and job opportunities. This paper examines employment accessibility in Nairobi, Kenya and evaluates whether modification of land use patterns can contribute to increases in aggregate accessibility. The assessment is based on simulation of counterfactual scenarios of the location of jobs and households throughout the city without new investments in housing or transport infrastructure. The analysis finds that modifications to the spatial layout of Nairobi that encourage land use clustering can increase the share of overall opportunities that can be accessed within a given time-frame. When commuters travel by foot or using the minibus network, the share of accessible economic opportunities within an hour doubles from 11 to 21 percent and from 20 to 42 percent respectively. The analysis also finds that spatial layouts that maximize the number of households that have access to a minimum share of jobs, through a more even jobs-housing balance, come at the expense of average accessibility. This result is interpreted as a trade-off between inclusive and efficient labor markets. Document type: Boo

Carbon Price Efficiency Lock-in and Path Dependence in Urban Forms and Transport Infrastructure

International audienceThis paper investigates the effect of carbon or gasoline taxes on commuting-related CO2 emissions in an urban context. To assess the impact of public transport on the efficiency of the tax, the paper investigates two exogenous scenarios using a dynamic urban model (NEDUM-2D) calibrated for the urban area of Paris: (i) a scenario with the current dense public transport infrastructure, and (ii) a scenario without. It is shown that the price elasticity of CO2 emissions is twice as high in the short run if public transport options exist. Reducing commuting-related emissions thus requires lower (and more acceptable) tax levels in the presence of dense public transportation. The emission elasticity also depends on the baseline scenario (especially population and income growth) and increases over time. In the longer run, elasticities are similar in the scenarios with and without public transport, due to larger urban reconfiguration in the latter scenario. This analysis may help calibrate general equilibrium models by providing price elasticities that depend on socio-economic and public transport infrastructure scenarios. If the goal of a carbon or gasoline tax is to change behaviors and reduce energy consumption and CO2 emissions (not to raise revenues), then there is an incentive to increase the price elasticity through complementary policies such as innovation support and infrastructure development

Modélisation de l’effet d’une taxe sur la construction : le Versement pour Sous-Densité

National audienceLe Versement pour Sous Densité est une mesure innovante qui a fait son entrée dans la loi française depuis mi-2012 et qui vise à limiter l’étalement urbain en taxant les nouvelles constructions qui n’atteignent pas un Seuil minimal de densité. Ce papier, à travers l’utilisation d’un modèle transportusage des sols (NEDUM 2D), quantifie les impacts potentiels de cette politique sur l’Ile-de-France et examine les conditions qui lui permettraient de gagner en efficacité tout en limitant les coûts sociaux de sa mise en œuvre. Les résultats de cette étude montrent que si cet outil est correctement utilisé, il peut contribuer à limiter l’étalement urbain tout en augmentant les surfaces construites et donc en diminuant le niveau des prix immobiliers et des loyers. De façon surprenante, il s’agit donc d’une taxe sur la construction qui a pour résultat un accroissement des surfaces des logements. Cependant la mise en œuvre de cette politique est compliquée puisque le choix du Seuil minimal de densité en conditionne largement l’efficacité. Si celui-ci est trop bas le versement peut avoir des impacts contre-productifs comme une accélération de l’étalement urbain. De plus, en fonction de l’objectif privilégié (limitation de l’étalement urbain, accès aux transports en commun, …), le choix du seuil optimal variera

Quels outils pour éclairer les décisions des collectivités locales dans le domaine du climat ?

L'urgence climatique appelle des politiques de réduction de gaz à effet de serre ambitieuses. Depuis la mise en oeuvre du protocole de Kyoto les avancées sont réelles avec notamment la création du marché carbone européen (EU ETS) pour les entreprises fortement émettrices. Cependant, il apparaît aujourd'hui que cette direction ne peut à elle seule suffire à placer les économies sur des sentiers de croissance suffisamment vertueux. Dans ce contexte, les villes qui sont les hôtes principaux des populations (plus de 50% de la planète vit en zone urbaine depuis 2007) et des activités consommatrice d'énergie (transport, bâtiment...), apparaissent comme une « nouvelle » aire d'investigation pour les politiques climatiques constituant d'immenses potentialités de réduction de gaz à effet de serre. De nombreux territoires sont convaincus de leur rôle fondamental dans la bataille du climat et tendent à se regrouper et à s'engager dans des plans climat locaux que des éclairages scientifiques pourraient contribuer à rendre plus efficaces. L'émergence de la ville / du territoire comme niveau approprié de mise en oeuvre des politiques climatiques, impose aux chercheurs de renouveler outils et approches méthodologiques afin de pouvoir rendre compte des nouvelles options techniques et organisationnelles et éclairer la décision politique. Ce chapitre explore les pistes d'amélioration possibles des outils de prospective dans le domaine énergie – climat, pour apporter aux collectivités territoriales des éclairages appropriés à des politiques climatiques locales plus ambitieuses.DEVELOPPEMENT DURABLE ; POLITIQUE LOCALE ; VILLE

Different paths to the modern state in Europe: the interaction between domestic political economy and interstate competition

Theoretical work on state formation and capacity has focused mostly on early modern Europe and on the experience of western European states during this period. While a number of European states monopolized domestic tax collection and achieved gains in state capacity during the early modern era, for others revenues stagnated or even declined, and these variations motivated alternative hypotheses for determinants of fiscal and state capacity. In this study we test the basic hypotheses in the existing literature making use of the large date set we have compiled for all of the leading states across the continent. We find strong empirical support for two prevailing threads in the literature, arguing respectively that interstate wars and changes in economic structure towards an urbanized economy had positive fiscal impact. Regarding the main point of contention in the theoretical literature, whether it was representative or authoritarian political regimes that facilitated the gains in fiscal capacity, we do not find conclusive evidence that one performed better than the other. Instead, the empirical evidence we have gathered lends supports to the hypothesis that when under pressure of war, the fiscal performance of representative regimes was better in the more urbanized-commercial economies and the fiscal performance of authoritarian regimes was better in rural-agrarian economie

Urban access across the globe: an international comparison of different transport modes

ABSTRACT: Access (the ease of reaching valued destinations) is underpinned by land use and transport infrastructure. The importance of access in transport, sustainability, and urban economics is increasingly recognized. In particular, access provides a universal unit of measurement to examine cities for the efficiency of transport and land-use systems. This paper examines the relationship between population-weighted access and metropolitan population in global metropolitan areas (cities) using 30-min cumulative access to jobs for 4 different modes of transport; 117 cities from 16 countries and 6 continents are included. Sprawling development with the intensive road network in American cities produces modest automobile access relative to their sizes, but American cities lag behind globally in transit and walking access; Australian and Canadian cities have lower automobile access, but better transit access than American cities; combining compact development with an intensive network produces the highest access in Chinese and European cities for their sizes. Hence density and mobility co-produce better access. This paper finds access to jobs increases with populations sublinearly, so doubling the metropolitan population results in less than double access to jobs. The relationship between population and access characterizes regions, countries, and cities, and significant similarities exist between cities from the same country

Mechanical and Assembly Units of Viral Capsids Identified via Quasi-Rigid Domain Decomposition

Key steps in a viral life-cycle, such as self-assembly of a protective protein container or in some cases also subsequent maturation events, are governed by the interplay of physico-chemical mechanisms involving various spatial and temporal scales. These salient aspects of a viral life cycle are hence well described and rationalised from a mesoscopic perspective. Accordingly, various experimental and computational efforts have been directed towards identifying the fundamental building blocks that are instrumental for the mechanical response, or constitute the assembly units, of a few specific viral shells. Motivated by these earlier studies we introduce and apply a general and efficient computational scheme for identifying the stable domains of a given viral capsid. The method is based on elastic network models and quasi-rigid domain decomposition. It is first applied to a heterogeneous set of well-characterized viruses (CCMV, MS2, STNV, STMV) for which the known mechanical or assembly domains are correctly identified. The validated method is next applied to other viral particles such as L-A, Pariacoto and polyoma viruses, whose fundamental functional domains are still unknown or debated and for which we formulate verifiable predictions. The numerical code implementing the domain decomposition strategy is made freely available

Energy Demand and Temperature: A Dynamic Panel Analysis

This paper is a first attempt to investigate the effect of climate on the demand for different energy vectors from different final users. The ultimate motivation for this is to arrive to a consistent evaluation of the impact of climate change on key consumption goods and primary factors such as energy vectors. This paper addresses these issues by means of a dynamic panel analysis of the demand for coal, gas, electricity, oil and oil products by residential, commercial and industrial users in OECD and (a few) non-OECD countries. It turns out that temperature has a very different influence on the demand of energy vectors as consumption goods and on their demand as primary factors. In general, residential demand responds negatively to temperature increases, while industrial demand is insensitive to temperature increases. As to the service sector, only electricity demand displays a mildly significant negative elasticity to temperature changes