Time to Dropout From College: A Hazard Model with Endogenous Waiting

Using data from the 1979 National Longitudinal Survey of Youth (NLSY79), we investigate the college attendance, dropout, and graduate behavior of high school graduates. Bivariate duration models, which allow the unobserved determinants of spell durations to be correlated across spells, are developed and used to study the impact of the waiting time from high school graduation until college enrollment on college dropout and graduation rates. We find that delaying college entry after graduating high school significantly increases the chances of college dropout and reduces the probability of attaining a four-year degree. Among those who first enroll in four-year institutions, delaying college entry by one year after high school graduation reduces the probability of graduating with a four- year degree by up to 32 percent in models that account for the endogeneity of delaying enrollment. There is also empirical evidence that the negative impact of delayed enrollment on graduation probabilities varies by Armed Forces Qualifying Test (AFQT) score with the largest estimated impact of delaying occurring for those with low AFQT scores.

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

The Union Membership Wage Premium for Employees Covered by Collective Bargaining Agreements.

Using Current Population Survey data for 1983-93, this article analyzes whether there is a union membership wage premium among full-time, private sector employees covered by union contracts. Ordinary least squares estimates of the membership wage premium are 12%-14%, and allowing membership to be endogenous yields larger estimates. Differences in job tenure, unobservable characteristics, and measurement error cannot fully explain the estimated premium. Significant differences in this premium, as well as in membership rates conditional upon coverage, across various demographic subgroups are also documented. In general, "free riders" do not appear to be free riding. Copyright 2000 by University of Chicago Press.