Econometric analyses of treatment response commonly use instrumental variable (IV) assumptions to identify treatment effects. Yet the credibility of IV assumptions is often a matter of considerable disagreement, with much debate about whether some covariate is or is not a 'valid instrument' in...

We examine the implications of arbitrage in a market with many assets. The absence of arbitrage opportunities implies that the linear functionals that give the mean and cost of a portfolio are continuous; hence there exist unique portfolios that represent these functionals. The mean variance...

This study presents a general methodology for fitting multiple time series models to panel data. The basic statistical framework considered here consists of a dynamic simultaneous equation model where disturbances follow a permanent-transitory scheme with transitory components generated by a...

This paper formulates an empirical model of consumption and labor supply that explicitly incorporates income taxes in a multiperiod setting. This model relies on few assumptions and provides a robust framework for estimating parameters needed to predict the response of consumption and hours of...

This paper formulates and estimates a structural life cycle model of labor supply. Using theoretical characterizations derived from an economic model of life cycle behavior, a two-stage empirical analysis yields estimates of intertemporal and uncompensated substitution effects which provides the...

This paper examines the economics of investing the central trust fund of Social Security in private securities. We note that switching from a policy of having the trust fund invest solely in special issue Treasury bonds to one where some of the portfolio holds common stocks amounts to an asset...

This paper surveys new methods for estimatifg labor supply functions. A unified framework of analysis is presented. All recent models of labor supply are special cases of a general index function model developed for the analysis o dummy endogenous variables

It is well known that disability rates among the American elderly have declined over the past decades. The cause of this decline is less well established. In this paper, we test one important possible explanation--that the decline in disability occurred because of chronic disease prevention...

In recent years, the use of Medicare-covered home health care and hospice services has grown dramatically. Hospice care, like much home health and nonacute hospital care, is designed to meet the needs of dying patients, who are known to generate disproportionately large costs of care. How has...

The highly uneven distribution of Medicare payments among elderly beneficiaries, combined with the predictability of some of the expenditures, poses several challenges to the Medicare program. We present information about the distribution of Medicare expenditures among beneficiaries in specific...