理论论文

Using the Uganda National Panel Survey, I document that farmers face a trade-off between crop yields and risk, that most grow both high- and low-yield crops, and that poorer farmers concentrate on the low-yield, low-risk ones. I then develop an incomplete-markets model with a crop-portfolio choice, in which households trade off income returns against consumption smoothing. Wealth-poor households optimally under-invest in intermediates and shift toward safer crops. Crop portfolios, intermediate input use, and the wealth distribution are jointly determined in equilibrium. The model also reproduces the low pass-through of both income inequality and income volatility into consumption. Calibrated to rural Uganda, it implies that completing markets raises agricultural productivity by 12.8%, with 15.8% of the gain coming from eliminating the misallocation of inputs across farmers and crops. Consumption rises by 17.6% and welfare by 17.4%, with income inequality rising slightly and consumption inequality unchanged.

Which countries drive global inequality? Which states drive US inequality? We characterize the class of inequality measures that can answer these questions, permitting both an additive decomposition by subgroup and a multiplicative decomposition into within- and between-group components. Its central measure is simply the expected ratio of incomes between two randomly selected individuals. We show that global inequality fell since 1990, driven by declining disparities between countries. Inequality is primarily driven by large middle-income countries (India, China) and poor countries (Democratic Republic of Congo, Ethiopia). In the US, rising inequality is explained by widening gaps within states, while between-state inequality remains limited.