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What are the consequences of a nationwide reform of a transfer system based on means-testing toward one of unconditional transfers? I answer this question with a quantitative model to assess the general equilibrium, inequality, and welfare effects of substituting the current US income security system with a universal basic income (UBI) policy. To do so, I develop an overlapping generations model with idiosyncratic income risk that incorporates intensive and extensive margins of the labor supply, on-the-job learning, and child-bearing costs. The tax-transfer system closely mimics the US design. I calibrate the model to the US economy and conduct counterfactual analyses that implement reforms toward a UBI. I find that an expenditure-neutral reform has moderate impacts on agents’ labor supply response but induces aggregate capital and output to grow due to larger precautionary savings. A UBI of $1,000 monthly requires a substantial increase in the tax rate of consumption used to clear the government budget and leads to an overall decrease in the macroeconomic aggregates, stemming from a drop in the labor supply. In both cases, the economy has more equally distributed disposable income and consumption. The UBI economy constitutes a welfare loss at the transition if it is expenditure-neutral and results in a gain in the second scenario.

This thesis focuses on how the design of public insurance policies entails distributional consequences that impact macroeconomic aggregates, inequality, and welfare.The first chapter assesses the general equilibrium effects of substituting the current U.S. income security system with a Universal Basic Income (UBI) policy. I develop an overlapping generations model with idiosyncratic income risk that incorporates intensive and extensive margins of labor supply, on-the-job learning, and child-bearing costs. I calibrate the model to the U.S. and conduct counterfactual analyses that implement reforms towards a UBI. I find that an expenditure-neutral reform has moderate impacts on agents' labor supply response but induces aggregate capital and output to grow due to larger precautionary savings. A UBI of $1,000 monthly requires a substantial increase in the tax rate of consumption used to clear the government budget and lead to an overall decrease in the aggregates. In both cases, the economy has more disposable income but less consumption at the bottom of their distributions. The UBI economy constitutes a welfare loss at the transition if expenditure-neutral and results in a gain in the second scenario. Despite relative losses, a majority of newborn households support both UBI reforms.The second chapter develops a heterogeneous agents model with history-dependent U.I. benefits built on stylized facts of the U.S. economy to quantitatively obtain an optimal U.I. program design. We first conduct an empirical analysis using the discontinuity of U.I. rules at state borders and find that a tenure requirement induces a longer employment spell. The monetary requirement decreases the number of employers and has a stronger effect on U.I. applications. The model can recover the sign of the relation between the requirements and the employment outcomes. When the tenure requirement is long, workers tend to accept more low paying jobs to become eligible sooner to U.I. and protect themselves from risk. The monetary requirement has the opposite effect. Due to its impact on moral hazard, the monetary requirement can generate higher levels of welfare than an increase in the length of the tenure requirement. The highest level of welfare is achieved by the optimization of both requirements.

Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community‐led open‐source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).Time period and grain: BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.