We develop a theory of political transitions inspired by the experiences of Western Europe and Latin America. Nondemocratic societies are controlled by a rich elite. The initially disenfranchised poor can contest power by threatening revolution, especially when the opportunity cost is low, for example, during recessions. The threat of revolution may force the elite to democratize. Democracy may not consolidate because it is redistributive, and so gives the elite an incentive to mount a coup. Highly unequal societies are less likely to consolidate democracy, and may end up oscillating between regimes and suffer substantial fiscal volatility.

Per-capita income in many sub-Saharan African countries, such as Chad and Niger, is less than 1/30th of that of the United States. Most economists and social scientists suspect that this is in part due to institutional failures that stop these societies from adopting the best technologies. A particularly interesting historical example comes from the di®usion of railways in the nineteenth century. While railways are regarded as a key technology driving the industrial revolution, there were large lags in its di®usion. For example, in 1850 the United States had 14,518km of track, Britain 9,797km and Germany 5,856km, in the Russian and Hapsburgh Empires there were just 501km and 1,357km, respectively (all data from Mitchell, 1993). Why do societies, as in this example, fail to adopt the best available technologies? One answer is that existing powerful `interest groups ' block the introduction of new technologies in order to protect their economic rents, and societies are able to make technological advances only if they can defeat such groups. Economic monopolies may be one example. A monopolist might wish to block the intro-

In the human capital model with perfect labor markets, firms never invest in general skills and all cost of general training are borne by workers. When lobor market frictions compress the structure of wages, firms may pay for these investments. The distortion in the wage structure turns "technologically" general skills into de facto "specific " skills. Credit market imperfections are neither neccessary nor sufficient for firm‐sponsored training. Since labor market frictions and insititutions shape the wage structure, they may have an important impact on the financing and amount of human capital investments and account for some international differences in training practices.

Unprecedented street protests brought down Mubarak's government and ushered in an era of competition between three rival political groups in Egypt. Using daily variation in the number of protesters, we document that more intense protests are associated with lower stock market valuations for firms connected to the group currently in power relative to non-connected firms, but have no impact on the relative valuations of firms connected to rival groups. These results suggest that street protests serve as a partial check on political rent-seeking. General discontent expressed on Twitter predicts protests but has no direct effect on valuations.

We study the determinants of vertical integration in a new data set of over 750,000 firms from 93 countries. We present a number of theoretical predictions on the interactions between financial development, contracting costs, and the extent of vertical integration. Consistent with these predictions, contracting costs and financial development by themselves appear to have no effect on vertical integration. However, we find greater vertical integration in countries that have both greater contracting costs and greater financial development. We also show that countries with greater contracting costs are more vertically integrated in more capital‐intensive industries.

Robert Gordon's The Rise and Fall of American Economic Growth compellingly shows how technical innovation, stimulated by the country's institutions, has radically improved the living standards of the citizens of the US. We conduct an empirical investigation of the impact of the capacity of the US state, as proxied by the presence of post offices, on innovation. We show that there is a strong association between the number of post offices in a county and patenting activity. Our evidence suggests that part of story of US innovation is the capacity and reach of the US state.

Internet-based educational resources are proliferating rapidly. One concern associated with these (potentially transformative) technological changes is that they will be disequalizing—as many technologies of the last several decades have been—creating superstar teachers and a winner-take-all education system. These important concerns notwithstanding, we contend that a major impact of web-based educational technologies will be the democratization of education: educational resources will be more equally distributed, and lower-skilled teachers will benefit. At the root of our results is the observation that skilled lecturers can only exploit their comparative advantage if other teachers complement those lectures with face-to-face instruction. This complementarity will increase the quantity and quality of face-to-face teaching services, potentially increasing the marginal product and wages of lower-skill teachers.

We present a model of online content sharing where agents sequentially observe an article and decide whether to share it with others. This content may or may not contain misinformation. Each agent starts with an ideological bias and gains utility from positive social media interactions but does not want to be called out for propagating misinformation. We characterize the (Bayesian–Nash) equilibria of this social media game and establish that it exhibits strategic complementarities. Under this framework, we study how a platform interested in maximizing engagement would design its algorithm. Our main result establishes that when the relevant articles have low-reliability and are thus likely to contain misinformation, the engagement-maximizing algorithm takes the form of a “filter bubble”—creating an echo chamber of like-minded users. Moreover, filter bubbles become more likely when there is greater polarization in society and content is more divisive. Finally, we discuss various regulatory solutions to such platform-manufactured misinformation.

Medical innovations during the 1940s quickly resulted in significant health improvements around the world. Countries with initially higher mortality from infectious diseases experienced larger increases in life expectancy, population, and subsequent social conflict. This cross-country result is robust across alternative measures of conflict and is not driven by differential trends between countries with varying baseline characteristics. A similar effect is also present within Mexico. Initial suitability conditions for malaria varied across municipalities, and anti-malaria campaigns had differential effects on population growth and social conflict. Both across countries and within Mexico, increased conflict over scarce resources predominates and this effect is more pronounced during times of economic hardship (specifically, in countries with a poor growth record and in drought-stricken areas in Mexico). At least during this time period, a larger increase in population made social conflict more likely.