Stephen H. Shore

Semiparametric Bayesian Modeling of Income Volatility Heterogeneity

Research on income risk typically treats its proxy—income volatility, the expected magnitude of income changes—as if it were unchanged for an individual over time, the same for everyone at a point in time, or both. In reality, income risk evolves over time, and some people face more of it than others. To model heterogeneity and dynamics in (unobserved) income volatility, we develop a novel semiparametric Bayesian stochastic volatility model. Our Markovian hierarchical Dirichlet process (MHDP) prior augments the recently developed hierarchical Dirichlet process (HDP) prior to accommodate the serial dependence of panel data. We document dynamics and substantial heterogeneity in income volatility.

The Intergenerational Transmission of Income Volatility: Is Riskiness Inherited?

This article examines the intergenerational transmission of income risk. Do risky parents have risky kids? Income volatility—a proxy for income risk—is not observed directly; instead, it must be estimated with substantial error from the time series variability of income. I characterize an income process with individual-specific volatility parameters and estimate the joint distribution of volatility parameters for fathers and for their adult sons. In data from the Panel Study of Income Dynamics, fathers with higher income volatility have sons with higher income volatility. This finding is correlated with, but far from fully explained by, the intergenerational transmission of risk tolerance and of the propensity for self-employment.

The Effect of Negative Equity on Mortgage Default: Evidence from HAMP PRA

The Home Affordable Modification Program’s Principal Reduction Alternative (HAMP PRA) is a government-sponsored program to reduce the principal balances and monthly mortgage payments of borrowers with negative equity (mortgage balances in excess of their home value, or “under water”) who are in danger of default. We use administrative data to examine the impact of principal forgiveness — a permanent mortgage balance reduction — on borrowers’ subsequent mortgage default. The program’s rules imply a kink in the relationship between principal forgiveness and a borrower’s initial equity level ceteris paribus. Our identification strategy exploits the quasi-experimental variation in principal forgiveness generated by this kink using a regression kink design (RKD), which compares the relationship between initial equity and default on either side of the kink. The quarterly hazard — the proportion of loans that become more than 90 days delinquent and consequently exit the program — in our sample is 3.1 percent; we estimate that it would have been 3.8 percent absent principal forgiveness, which averaged 28 percent of the initial mortgage balance.

Liquidity Constraints and Credit Card Delinquency: Evidence from Raising Minimum Payments

We use credit card data to estimate the impact of increasing minimum payments on delinquency, payments, spending, and write-offs. Our identification strategy exploits an unusual institutional feature: Borrowers can use their account to make purchases with both revolving loans (on which minimum payments increased) and term loans (on which there was no change). Payment increases by delinquent borrowers are insufficient to match increasing minimums, resulting in lower cure rates and an increase in write-offs. Affected borrowers migrate away from these accounts by decreasing charges and increasing payments, consequently lowering the interest earned by the bank.

Identifying Idiosyncratic Career Taste and Skill with Income Risk

How important to well-being is choosing a career with the right fit? This question is difficult to answer because we observe individuals only in their chosen careers, not in the other (presumably inferior) options they did not choose. To overcome this problem, we use expected utility to cardinalize a logit model of career choice in a setting where we observe the income risk of chosen careers and the risk-aversion of the people who choose them. The key parameter of interest - the importance of idiosyncratic taste and skill in career choice - is identified from the shift in the distribution of income risk with risk aversion. We estimate the model using individual-specific measures of income volatility to proxy for income risk and survey questions about hypothetical income gambles to proxy for risk preference, both from the PSID. We separate idiosyncratic career taste from skill using the pay gap between highand low-income risk people with high and low risk-aversion.