Migration, urban population growth and regional disparity in China

The main objective of this paper is to study the determinants of city population growth in China during the 1990s', as well as the determinants of migrations towards cities, which constitutes the main source of urban population growth in this period. A second objective is to identify regional differences in the urban growth and migrations, that is, whether urban growth and migration patterns are different between coastal and inland provinces. Additionally, we are interested in the differences between temporary and permanent migrations towards urban areas.cerdi

Migration, urban population growth and regional disparity in China

The main objective of this paper is to study the determinants of city population growth in China during the 1990s’, as well as the determinants of migrations towards cities, which constitutes the main source of urban population growth in this period. A second objective is to identify regional differences in the urban growth and migrations, that is, whether urban growth and migration patterns are different between coastal and inland provinces. Additionally, we are interested in the differences between temporary and permanent migrations towards urban areas.

Language Agents with Reinforcement Learning for Strategic Play in the Werewolf Game

Agents built with large language models (LLMs) have shown great potential across a wide range of domains. However, in complex decision-making tasks, pure LLM-based agents tend to exhibit intrinsic bias in their choice of actions, which is inherited from the model's training data and results in suboptimal performance. To develop strategic language agents, i.e., agents that generate flexible language actions and possess strong decision-making abilities, we propose a novel framework that powers LLM-based agents with reinforcement learning (RL). We consider Werewolf, a popular social deduction game, as a challenging testbed that emphasizes versatile communication and strategic gameplay. To mitigate the intrinsic bias in language actions, our agents use an LLM to perform deductive reasoning and generate a diverse set of action candidates. Then an RL policy trained to optimize the decision-making ability chooses an action from the candidates to play in the game. Extensive experiments show that our agents overcome the intrinsic bias and outperform existing LLM-based agents in the Werewolf game. We also conduct human-agent experiments and find that our agents achieve human-level performance and demonstrate strong strategic play

Accelerate Multi-Agent Reinforcement Learning in Zero-Sum Games with Subgame Curriculum Learning

Learning Nash equilibrium (NE) in complex zero-sum games with multi-agent reinforcement learning (MARL) can be extremely computationally expensive. Curriculum learning is an effective way to accelerate learning, but an under-explored dimension for generating a curriculum is the difficulty-to-learn of the subgames -- games induced by starting from a specific state. In this work, we present a novel subgame curriculum learning framework for zero-sum games. It adopts an adaptive initial state distribution by resetting agents to some previously visited states where they can quickly learn to improve performance. Building upon this framework, we derive a subgame selection metric that approximates the squared distance to NE values and further adopt a particle-based state sampler for subgame generation. Integrating these techniques leads to our new algorithm, Subgame Automatic Curriculum Learning (SACL), which is a realization of the subgame curriculum learning framework. SACL can be combined with any MARL algorithm such as MAPPO. Experiments in the particle-world environment and Google Research Football environment show SACL produces much stronger policies than baselines. In the challenging hide-and-seek quadrant environment, SACL produces all four emergent stages and uses only half the samples of MAPPO with self-play. The project website is at https://sites.google.com/view/sacl-rl

Urbanisation et Croissance des Villes en Chine

This dissertation studies urbanization and city growth in China. It is composed of tow parts. The first part begins with a review of theoretic models of urbanization in development economics, and then describes stylised facts of China's urbanization process. Problems of urban population measures, the unique industrialization strategies as well as institutional changes that determine urban growth are examined. The second part studies the link between city growth and agglomeration economies. The concept of agglomeration economies is clarified before we carry out empirical tests with a panel of about 150 Chinese cities in the 1990s. Then, the evolution of China's city size distribution is examined using different analysis approaches such as Zipf's law, Markov transition matrix. Finally, we estimate the determinants of city growth in the 1990s.Our finding suggests that urbanization process had been delayed in China, due to particular strategies of industrialisation (heavy industry bias before the reforms and rural industrialization after the reforms) and incomplete features of factor markets (labour and land); in particular, restrictive policies make that cities are not large enough to exploit gains related to agglomeration economies. With the deepening of its economic reforms, China would continue its structural transition from rural to urban society, and urban growth would be one of the driving forces of China's economic growth. Policies aimed at promoting urbanization and growth should consist in relaxing the restrictions on city size, establishing complete product and factor market, and improving urban governance, especially the provision of urban infrastructures.Cette thèse étudie l'urbanisation et la croissance des villes en Chine. Elle est composée de deux parties : la première partie est consacrée à une revue des modèles théoriques d'urbanisation et à une description de l'urbanisation de la Chine. Le problème de la mesure de la population urbaine, des changements institutionnels ainsi que des spécificités du processus d'urbanisation chinois sont étudiés. La deuxième partie relie la croissance économique urbaine aux économies d'agglomération, et étudie les caractéristiques de la croissance récente de la population des villes. Le concept théorique d'économie agglomération est clarifié avant de procéder à des tests empiriques sur une base de données d'environ 150 villes chinoises pendant la décennie 1990. En suite, nous examinons l'évolution de la distribution de la taille des villes par différents instruments d'analyse. Enfin, nous estimons les déterminants de la croissance urbaine durant la période 1990-2000.Notre étude suggère que la Chine a connu un retard de l'urbanisation dû aux stratégies d'industrialisation particulières (biais de l'industrie lourde avant les réformes et industrialisation rurale après les réformes) et au caractère incomplet des marchés des facteurs de production (le travail et la terre, entre autres) ; les villes ne sont pas assez grandes pour exploiter les économies d'agglomération. Avec l'approfondissement des réformes économiques, la Chine doit poursuivre cette transformation structurelle rurale/urbaine car le développement de l'économie urbaine va constituer l'un des moteurs de la croissance économique du pays. Les politiques destinées à promouvoir l'urbanisation doivent consister à améliorer les institutions sur les marchés des facteurs de production, et à relâcher les restrictions sur la taille des villes

Productivity and Agglomeration Economies in Chinese Cities

I test the existence of agglomeration economies in Chinese cities by evaluating the impact of population size and density on urban productivity. Based on panel data of about 150 Chinese cities during the 1990s, I find an inverted U-shaped relationship between city size and productivity as well as a positive effect of population density on urban productivity. The estimated city size corresponding to the peak point of labour productivity ranges between 3 and 4 million, which implies that most cities in our sample are not large enough to fully exploit productivity advantages associated with agglomeration economies. Comparative Economic Studies (2009) 51, 284–301. doi:10.1057/ces.2008.43; published online 21 May 2009

Migration, urban population growth and regional disparity in China

The main objective of this paper is to study the determinants of city population growth in China during the 1990s', as well as the determinants of migrations towards cities, which constitutes the main source of urban population growth in this period. A second objective is to identify regional differences in the urban growth and migrations, that is, whether urban growth and migration patterns are different between coastal and inland provinces. Additionally, we are interested in the differences between temporary and permanent migrations towards urban areas

City size distribution in China: are large cities dominant?

This paper examines the evolution in size distribution of Chinese cities. Since the relaxation of restrictions on rural/urban migration in the 1980s, China has experienced rapid urban growth. However, cities of different sizes have experienced varying patterns of growth. We first describe the evolution of city size distribution in China by documenting the growth both of city size and of the number of existing cities. Then, focusing on the period from 1990-2000, we characterize the urban evolution trend with the Pareto law estimation, and examine the mobility of cities between different size groups with the Markov transition matrix. We also test the convergence hypothesis in the city population growth process. Our results suggest that, contrary to the expected dominance of large cities' growth, Chinese city size distribution evened out over the 1990s, with small cities growing more rapidly than large cities