This paper's findings suggest that an arbitrary Chinese policy that greatly increases total suspended particulates (TSPs) air pollution is causing the 500 million residents of Northern China to lose more than 2.5 billion life years of life expectancy. The quasi-experimental empirical approach is based on China's Huai River policy, which provided free winter heating via the provision of coal for boilers in cities north of the Huai River but denied heat to the south. Using a regression discontinuity design based on distance from the Huai River, we find that ambient concentrations of TSPs are about 184 μg/m 3 [95% confidence interval (CI): 61, 307] or 55% higher in the north. Further, the results indicate that life expectancies are about 5.5 y (95% CI: 0.8, 10.2) lower in the north owing to an increased incidence of cardiorespiratory mortality. More generally, the analysis suggests that long-term exposure to an additional 100 μg/m 3 of TSPs is associated with a reduction in life expectancy at birth of about 3.0 y (95% CI: 0.4, 5.6).airborne particulate matter | unintended consequences of policy | premature mortality | health costs of coal combustion | Chinese environmental quality

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Social learning has attracted increasing attention in the economics literature. The general concept of social learning encompasses many mechanisms through which individuals may learn from others. In particular, it includes the mechanism in which individuals learn from each other through direct (formal or informal) communications; it also includes the mechanism of observational learning where the behavior of individuals is influenced by their observation of other people's choices because of the information contained therein. 1Convincing empirical evidence about the importance of observational learning is not only relevant for the theoretical literature in economics; it also has policy implications. The key difference between direct communications and observational learning as channels of social learning lies in whether temporal, spatial, and social proximity among individuals is important for learning to occur. Observational learning can take place as long as the underlying decision problems faced by individuals are similar; in contrast, learning from others via direct communications requires individuals to be close in time, space, and social distance. As a result, if a policy maker wants to, say, expedite the adoption of an advantageous technology, an information campaign about the technology's popularity among other groups of agents will be effective if observational learning is important, but will not be effective if, instead, direct communication is the main channel of social learning.1 Albert Bandura (1977) wrote the pioneering book in psychology that started the research on social and observational learning. Abhijit Banerjee (1992) andIvo Welch (1992) Durham, NC 27708-0097, NBER, and SHUFE (e-mail: hanming.fang@duke.edu). The Institute for Social and Policy Studies (ISPS) at Yale University funded this project. We are most grateful to Donald Green, Director of ISPS, for his important suggestions regarding the experimental design and general guidance about field experiments. We would also like to thank Paul Dudenhefer, Dean Karlan, Enrico Moretti, Emmanuel Saez, Lan Shi, and especially three anonymous referees and the coeditor for helpful comments. Finally, we thank the managers in Mei Zhou Dong Po restaurant chain for their enthusiastic participation and cooperation in this field experiment. All remaining errors are ours.

Lightweight, stretchable, and wearable strain sensors have recently been widely studied for the development of health monitoring systems, human-machine interfaces, and wearable devices. Herein, highly stretchable polymer elastomer-wrapped carbon nanocomposite piezoresistive core-sheath fibers are successfully prepared using a facile and scalable one-step coaxial wet-spinning assembly approach. The carbon nanotube-polymeric composite core of the stretchable fiber is surrounded by an insulating sheath, similar to conventional cables, and shows excellent electrical conductivity with a low percolation threshold (0.74 vol %). The core-sheath elastic fibers are used as wearable strain sensors, exhibiting ultra-high stretchability (above 300%), excellent stability (>10 000 cycles), fast response, low hysteresis, and good washability. Furthermore, the piezoresistive core-sheath fiber possesses bending-insensitiveness and negligible torsion-sensitive properties, and the strain sensing performance of piezoresistive fibers maintains a high degree of stability under harsh conditions. On the basis of this high level of performance, the fiber-shaped strain sensor can accurately detect both subtle and large-scale human movements by embedding it in gloves and garments or by directly attaching it to the skin. The current results indicate that the proposed stretchable strain sensor has many potential applications in health monitoring, human-machine interfaces, soft robotics, and wearable electronics.

We study the causal effect of school curricula on students' political attitudes, exploiting a major textbook reform in China between 2004 and 2010. The sharp, staggered introduction of the new curriculum across provinces allows us to identify its causal effects. We examine government documents articulating desired consequences of the reform, and identify changes in textbooks reflecting these aims. A survey we conducted reveals that the reform was often successful in shaping attitudes, while evidence on behavior is mixed. Studying the new curriculum led to more positive views of China's governance, changed views on democracy, and increased skepticism toward free markets.