On optimal heuristic randomized semidecision procedures, with application to proof complexity

The existence of a (p-)optimal propositional proof system is a major open question in (proof) complexity; many people conjecture that such systems do not exist. Krajicek and Pudlak (1989) show that this question is equivalent to the existence of an algorithm that is optimal on all propositional tautologies. Monroe (2009) recently gave a conjecture implying that such algorithm does not exist. We show that in the presence of errors such optimal algorithms do exist. The concept is motivated by the notion of heuristic algorithms. Namely, we allow the algorithm to claim a small number of false "theorems" (according to any samplable distribution on non-tautologies) and err with bounded probability on other inputs. Our result can also be viewed as the existence of an optimal proof system in a class of proof systems obtained by generalizing automatizable proof systems.Comment: 11 pages, accepted to STACS 201

Underpaid or Overpaid? Wage Analysis for Nurses Using Job and Worker Attributes

The nursing labor market presents an apparent puzzle. Hospitals report chronic shortages, yet standard wage analysis shows that nursing wages have increased over time and greatly exceed those received by other college-educated women. This paper addresses this puzzle. Data from the Current Population Survey (CPS) are matched with detailed job content descriptors from the Occupational Information Network (O*NET). Nursing jobs require higher levels of skills and more difficult working conditions than do jobs for other college educated workers. A standard CPS-only wage regression shows a registered nurse (RN) wage advantage of .22 log points compared to a pooled male/female group of college-educated workers. Control for O*NET job attributes reduces the RN gap to .08, while an arguably preferable nonparametric estimator produces a wage gap estimate close to zero. We conclude that nurses receive compensation close to long-run opportunity costs, narrowing if not resolving the RN wage-shortage puzzle.nursing, wage differentials, job attributes

Labor Earnings, Discrimination, and the Racial Composition of Jobs

This paper examines the effect of the racial composition of labor markets on wage rates and the racial wage gap. The wage rates of white as well as black workers are significantly lower in industry- occupation-regional groups with high densities of black workers, while the racial wage gap does not vary systematically with respect to racial density. Interpretation of racial gap estimates can be sensitive to inclusion of a racial density variable, particularly in sparse specifications. An explanation for the wagedensity relationship cannot be established, but results are most consistent with a quality sorting explanation and, to a lesser extent, the crowding hypothesis

Compensating Differentials and Unmeasured Ability in the Labor Market for Nurses: Why Do Hospitals Pay More?

Registered nurses (RNs) employed in hospitals realize a large wage advantage relative to RNs employed elsewhere. Cross-sectional estimates indicate a hospital RN wage advantage of roughly 20%. This paper examines possible sources of the hospital premium, a topic of some interest given the current shifting of medical care out of hospitals. Longitudinal analysis of Current Population Survey data for 1979-94 suggests that a third to a half of the advantage is due to unmeasured worker ability, and the authors conclude that the remainder of the advantage probably reflects compensating differentials for hospital disamenities. Supporting these conclusions is evidence that hospital RNs have higher cognitive ability and higher-quality job experience than non-hospital RNs, and indications that shift work accounts for roughly 10% of the hospital premium