Managing imperfect competition by pay for performance and reference pricing

I study a managed health service market where differentiated providers compete for consumers by choosing multiple service qualities, and where copayments that consumers pay and payments that providers receive for services are set by a payer. The optimal regulation scheme is two-sided. On the demand side, it justifies and clarifies value-based reference pricing. On the supply side, it prescribes pay for performance when consumers misperceive service benefits or providers have intrinsic quality incentives. The optimal bonuses are expressed in terms of demand elasticities, service technology, and provider characteristics. However, pay for performance may not outperform prospective payment when consumers are rational and providers are profit maximizing, or when one of the service qualities is not contractible

Zipfs Law for Cities: An Empirical Examination

We use data for metro areas in the United States, from the US Census for 1900 û 1990, to test the validity of Zipf's Law for cities. Previous investigations are restricted to regressions of log size against log rank. In contrast, we use a nonparametric procedure to calculate local Zipf exponents from the mean and variance of city growth rates. This also allows us to test for the validity of Gibrat's Law for city growth processes. Despite variation in growth rates as a function of city size, Gibrat's Law does hold. In addition the local Zipf exponents are broadly consistent with Zipf's Law. Deviations from Zipf's Law are easily explained by deviations from Gibrat's Law.Urban growth, Zipfs Law, Gibrats Law, estimation of Brownian motion

Spatial Evolution of the US Urban System

We test implications of economic geography models for location, size and growth of cities with US Census data for 1900 û 1990. Our tests involve non-parametric estimations of stochastic kernels for the distributions of city sizes and growth rates, conditional on various measures of market potential and on features sizes of neighbors. We show that while these relationships change during the twentieth century, by 1990 they stabilize such that the size distribution of cities conditional on a range of spatial variables are all roughly independent of these conditioning variables. In contrast, similar results suggest that there is a spatial element to the city wage distribution. Our parametric estimations for growth rates against market potential, entry of neighbors, and own lagged population imply a negative effect of market potential on growth rates, unless own lagged population is also included, in which case market potential has a positive effect and own lagged population a negative one. Cities grow faster when they are small relative to their market potential. In total, our results support some theoretical predictions, but also provide a number of interesting puzzles.Urban growth, spatial evolution, economic geography

Cross Sectional Evolution of the US City Size Distribution

We report nonparametrically estimated stochastic transition kernels for the evolution of the distribution of US metropolitan area populations, for the period 1900 to 1990. These suggest a fair amount of uniformity in the patterns of mobility during the study period. The distribution of city sizes is predominantly character-sed by persistence. Additional kernel estimates do not reveal any stark differences in intra-region mobility patterns. We characterise the nature of intra-size distribution dynamics by means of measures that do not require discretisation of the city size distribution. We employ these measures to study the degree of mobility within the US city size distribution and, separately, within regional and urban subsystems. We find that different regions show different degrees of intra-distribution mobility. Second-tier cities show more mobility than top-tier cities.City size distribution, cross-sectional evolution, intradistribution mobility

Design considerations for the airframe-integrated scramjet

Research programs at the NASA Langley Research Center on the development of airframe-integrated scramjet concepts (supersonic combustion ramjet) are reviewed briefly. The design and performance of a specific scramjet configuration are examined analytically by use of recently developed and substantiated techniques on boundary-layer development, heat transfer, fuel-air mixing, heat-release rates, and engine-cycle analysis. These studies indicate that the fixed-geometry scramjet module will provide practical levels of thrust performance with low cooling requirements. Areas which need particular emphasis in further development work are the combustor design for low speeds and the integrated nozzle design

Oscillator strengths for OII ions

Oscillator strengths between various doublet states of OII ions are calculated in which extensive multi-configuration wave functions are used. The lower levels for the transitions are of the 2p(3) D(2)o and 2p(3) 2po states, and the upper levels are 2p(4), 3s, and 3d states. The results, which are estimated to have errors of less than 10% for individual transitions, agree quite well with the beam foil experiments, as well as with the calculations by use of the non-closed shell many electron theory (NCMET). The agreement with the rocket measurements is also good except for the 538/581 A pair, in which the 538 A line is believed to be blend with the other stronger quartet line. However, a comparison with the recent branching ratio measurement indicates that discrepances between the present calculation and th experiment do exist for certain transistions