Essays on the Effects of Social Insurance for Disability

This dissertation examines how social insurance, family support and work capacity enhance individuals' economic well-being following significant health and income shocks. I first examine the extent to which the liquidity-enhancing effects of Worker's Compensation (WC) benefits outweigh the moral hazard costs. Analyzing administrative data from Oregon, I estimate a hazard model exploiting variation in the timing and size of a retroactive lump-sum WC payment to decompose the elasticity of claim duration with respect to benefits into the elasticity with respect to an increase in cash on hand, and a decrease in the opportunity cost of missing work. I find that the liquidity effect accounts for 60 to 65 percent of the increase in claim duration among lower-wage workers, but less than half of the increase for higher earners. Using the framework from Chetty (2008), I conclude that the insurance value of WC exceeds the distortionary cost, and increasing the benefit level could increase social welfare. Next, I investigate how government-provided disability insurance (DI) interacts with private transfers to disabled individuals from their grown children. Using the Health and Retirement Study, I estimate a fixed effects, difference in differences regression to compare transfers between DI recipients and two control groups: rejected applicants and a reweighted sample of disabled non-applicants. I find that DI reduces the probability of receiving a transfer by no more than 3 percentage points, or 10 percent. Additional analysis reveals that DI could increase the probability of receiving a transfer in cases where children had limited prior information about the disability, suggesting that DI could send a welfare-improving information signal. Finally, Zachary Morris and I examine how a functional assessment could complement medical evaluations in determining eligibility for disability benefits and in targeting return to work interventions. We analyze claimants' self-reported functional capacity in a survey of current DI beneficiaries to estimate the share of disability claimants able to do work-related activity. We estimate that 13 percent of current DI beneficiaries are capable of work-related activity. Furthermore, other characteristics of these higher-functioning beneficiaries are positively correlated with employment, making them an appropriate target for return to work interventions.

AN EXAMINATION OF HYDROXYL RADICAL: OUR CURRENT UNDERSTANDING OF THE OXIDATIVE CAPACITY OF THE TROPOSPHERE THROUGH EMPIRICAL, BOX, AND GLOBAL MODELING APPROACHES

Hydroxyl radical (OH) is the primary oxidant in the troposphere, initiating the removal of numerous atmospheric species including greenhouse gases, pollutants that are detrimental to human health, and ozone-depleting substances. Because of the complexity of OH chemistry, models vary widely in their OH chemistry schemes and resulting methane (CH4) lifetimes. The current state of knowledge concerning global OH abundances is often contradictory. This body of work encompasses three projects that investigate tropospheric OH from a modeling perspective, with the goal of improving the tropospheric community’s knowledge of the atmospheric lifetime of CH4. First, measurements taken during the airborne CONvective TRansport of Active Species in the Tropics (CONTRAST) field campaign are used to evaluate OH in global models. A box model constrained to measured variables is utilized to infer concentrations of OH along the flight track. Results are used to evaluate global model performance, suggest against the existence of a proposed “OH Hole” in the tropical Western Pacific, and investigate implications of high O3/low H2O filaments on chemical transport to the stratosphere. While methyl chloroform-based estimates of global mean OH suggest that models are overestimating OH, we report evidence that these models are actually underestimating OH in the tropical Western Pacific. The second project examines OH within global models to diagnose differences in CH4 lifetime. I developed an approach to quantify the roles of OH precursor field differences (O3, H2O, CO, NOx, etc.) using a neural network method. This technique enables us to approximate the change in CH4 lifetime resulting from variations in individual precursor fields. The dominant factors driving CH4 lifetime differences between models are O3, CO, and J(O3-O1D). My third project evaluates the effect of climate change on global fields of OH using an empirical model. Observations of H2O and O3 from satellite instruments are combined with a simulation of tropical expansion to derive changes in global mean OH over the past 25 years. We find that increasing H2O and increasing width of the tropics tend to increase global mean OH, countering the increasing CH4 sink and resulting in well-buffered global tropospheric OH concentrations.

EXISTENCE OF UNUSED MANAGED CAPACITY ON DEDICATED LANES AND AN ALTERNATIVE ON HOW TO SELL IT VIA AUCTIONS

This dissertation verifies whether the following two hypotheses are true: (1) High-occupancy/toll lanes (and therefore other dedicated lanes) have capacity that could still be used; (2) such unused capacity (or more precisely, “unused managed capacity”) can be sold successfully through a real-time auction. To show that the second statement is true, this dissertation proposes an auction-based metering (ABM) system, that is, a mechanism that regulates traffic that enters the dedicated lanes. Participation in the auction is voluntary and can be skipped by paying the toll or by not registering to the new system. This dissertation comprises the following four components: a measurement of unused managed capacity on an existing HOT facility, a game-theoretic model of an ABM system, an operational description of the ABM system, and a simulation-based evaluation of the system. Some other and more specific contributions of this dissertation include the following: (1) It provides a definition and a methodology for measuring unused managed capacity and another important variable referred as “potential volume increase”. (2) It proves that the game-theoretic model has a unique Bayesian Nash equilibrium. (3) And it provides a specific road design that can be applied or extended to other facilities. The results provide evidence that the hypotheses are true and suggest that the ABM system would benefit a public operator interested in reducing traffic congestion significantly, would benefit drivers when making low-reliability trips (such as work-to-home trips), and would potentially benefit a private operator interested in raising revenue.