Growth and Enduring Epidemic Diseases

This paper studies the formation of human capital and its transmission across generations when premature adult mortality is a salient feature of the demographic landscape, either permanently or in the form of a long-period wave that follows the outbreak of an epidemic. We establish several threshold properties of the model, for such a shock can severely retard economic growth, even to the point of leading to an economic collapse. Premature adult mortality may exacerbate inequality under nuclear family arrangements. Pooling mortality risks with equal treatment of all children may fend off, or even induce, a collapse, depending on the initial conditions and the size and duration of the shock. Awareness campaigns may also trigger a collapse by introducing undesirable expectational feedbacks.Epidemic Diseases, HIV/AIDS, Growth, Collapse, Pooling

Economic growth, education, and AIDS in Kenya : a long-run analysis

The AIDS epidemic threatens Kenya with a long wave of premature adult mortality, and thus with an enduring setback to the formation of human capital and economic growth. To investigate this possibility, the authors develop a model with three overlapping generations, calibrate it to the demographic and economic series from 1950 until 1990, and then perform simulations for the period ending in 2050 under alternative assumptions about demographic developments, including the counterfactual in which there is no epidemic. Although AIDS does not bring about a catastrophic economic collapse, it does cause large economic costs-and many deaths. Programs that subsidize post-primary education and combat the epidemic are both socially profitable-the latter strikingly so, due to its indirect effects on the expected returns to education-and a combination of the two interventions profits from a modest long-run synergy effect.Population Policies,Primary Education,Education For All,Adolescent Health,Economic Theory&Research

The long-run economic costs of AIDS : theory and an application to South Africa

Most existing estimates of the macroeconomic costs of AIDS, as measured by the reduction in thegrowth rate of gross domestic product, are modest. For Africa-the continent where the epidemic has hit the hardest-they range between 0.3 and 1.5 percent annually. The reason is that these estimates are based on an underlying assumption that the main effect of increased mortality is to relieve pressure on existing land and physical capital so that output per head is little affected. The authors argue that this emphasis is misplaced and that, with a more plausible view of how the economy functions over the long run, the economic costs of AIDS are almost certain to be much higher. Not only does AIDS destroy existing human capital, but by killing mostly young adults, it also weakens the mechanism through which knowledge and abilities are transmitted from one generation to the next. The children of AIDS victims will be left without one or both parents to love, raise, and educate them. The model yields the following results. In the absence of AIDS, the counterfactual benchmark, there is modest growth, with universal and complete education attained within three generations. But if nothing is done to combat the epidemic, a complete economic collapse will occur within three generations. With optimal spending on combating the disease, and if there is pooling, growth is maintained, albeit at a somewhat slower rate than in the benchmark case in the absence of AIDS. If pooling breaks down and is replaced by nuclear families, growth will be slower still. Indeed, if school attendance subsidies are not possible, growth will be distinctly sluggish. In all three cases, the additional fiscal burden of intervention will be large, which reinforces the gravity of the findings.Economic Theory&Research,Public Health Promotion,Labor Policies,Health Monitoring&Evaluation,Decentralization,Health Monitoring&Evaluation,Population&Development,Economic Theory&Research,Street Children,Adolescent Health

Raising Juveniles

This paper investigates how families make decisions about the education of juveniles. The decision problem is analyzed in three variations: a 'decentralized' scheme, in which the parents control the purse-strings, but the children dispose of their time as they see fit; a 'hierarchical' scheme, in which the parents can enforce a particular level of schooling by employing a monitoring technology; and the cooperative solution, in which the threat point is one of the two noncooperative outcomes. Adults choose which game is played. While the subgame perfect equilibrium of the overall game is Pareto-efficient when viewed statically, it may yield less education than the hierarchical scheme. Regulation in the form of restrictions on child labor and compulsory schooling generally affects both the threat point and the feasible set of bargaining outcomes, and families may choose more schooling than the minimum required by law.family decision-making, youth, human capital, bargaining

TMB: Automatic Differentiation and Laplace Approximation

TMB is an open source R package that enables quick implementation of complex nonlinear random effect (latent variable) models in a manner similar to the established AD Model Builder package (ADMB, admb-project.org). In addition, it offers easy access to parallel computations. The user defines the joint likelihood for the data and the random effects as a C++ template function, while all the other operations are done in R; e.g., reading in the data. The package evaluates and maximizes the Laplace approximation of the marginal likelihood where the random effects are automatically integrated out. This approximation, and its derivatives, are obtained using automatic differentiation (up to order three) of the joint likelihood. The computations are designed to be fast for problems with many random effects (~10^6) and parameters (~10^3). Computation times using ADMB and TMB are compared on a suite of examples ranging from simple models to large spatial models where the random effects are a Gaussian random field. Speedups ranging from 1.5 to about 100 are obtained with increasing gains for large problems. The package and examples are available at http://tmb-project.org

CHILD LABOR AND THE EDUCATION OF A SOCIETY

This paper analyzes policies by means of which a whole society in an initial state of illiteracy and low productivity can raise itself into a condition of continuous growth. Using an overlapping generations model in which human capital is formed through child rearing and formal education, we show that an escape from a poverty trap, in which children work full time and no human capital accumulation takes place, is possible through compulsory education or programs of taxes and transfers. If school attendance is unenforceable, temporary inequality is unavoidable if the society is to escape in finite time, but long-run inequalities are avoidable provided sufficiently heavy, but temporary, taxes can be imposed on the better off. Programs that aim simply at high attendance rates in the present can be strongly nonoptima

Violent Relaxation of Indistinguishable Objects and Neutrino Hot Dark Matter in Clusters of Galaxies

The statistical mechanical investigation of violent relaxation (Lynden-Bell 1967) is extended to indistinguishable objects. It is found that, coincidentally, the equilibrium distribution is the same as that obtained for classical objects. For massive neutrinos, the Tremaine \& Gunn (1979) phase space bound is revisited and reinterpretated as the limit indicating the onset of degeneracy related to the coarse-grained phase space distribution. In the context of one of the currently most popular cosmological models, the Cold and Hot Dark Matter (CHDM) model (Primack et al. 1995), the onset of degeneracy may be of importance in the core region of clusters of galaxies. Degeneracy allows the neutrino HDM density to exceed the limit imposed by the Tremaine \& Gunn (1979) bound while accounting for the phase space bound.Comment: AASTeX, 16 pages, 2 EPS figures, uses aas2pp4.sty. Accepted by ApJ Letter

Small Orbit Transfer Vehicle (OTV) for On-Orbit Satellite Servicing and Resupply

The field of on-orbit servicing of space systems has been studied extensively, and techniques for performing satellite resupply and repair functions have been developed in detail. They are covered extensively in the literature. Based on this background, Microcosm has performed design studies, partly under NASA/MSFC contract, of a small-size, 300 kg-class multi-function Orbital Transfer Vehicle (OTV) that can provide servicing and resupply functions for the International Space Station (ISS). It carries the required payload from a launch vehicle upper stage to the Station, and after berthing it supports servicing activities of the ISS crew members. The vehicle has a payload-carrying capability of 350 kg. The current design includes grappling fixtures specifically designed for ISS berthing which can be eliminated for servicing other satellites. The very strict safety requirements involving ISS access were taken into account in the servicing vehicle design. Repeated ISS servicing sorties to be performed by the OTV are of particular interest, to meet tight revisiting schedules. Extended reuse of the same OTV, once in orbit, allows substantial launch and operational cost savings. Propellant requirements for the servicing sorties are very modest, allowing an extended on-orbit life of this vehicle, with at least 3, but more likely 6 to 8 ISS revisits. The OTV discussed here can be utilized for low-cost servicing of other spacecraft as well. The paper discusses the vehicle’s maneuver sequences and propellant requirements, and describes its design features and its interactions with the ISS. The OTV’s total recurring cost is estimated at less than $35 Million. It would nominally be carried by a light-lift launcher, such as Microcosm’s planned Sprite vehicle, at a projected cost of the order of$2.5 Million

Major Merging: The Way to Make a Massive, Passive Galaxy

We analyze the projected axial ratio distribution, p(b/a), of galaxies that were spectroscopically selected from the Sloan Digital Sky Survey (DR6) to have low star-formation rates. For these quiescent galaxies we find a rather abrupt change in p(b/a) at a stellar mass of ~10^{11} M_sol: at higher masses there are hardly any galaxies with b/a<0.6, implying that essentially none of them have disk-like intrinsic shapes and must be spheroidal. This transition mass is ~3-4 times higher than the threshold mass above which quiescent galaxies dominate in number over star-forming galaxies, which suggests these mass scales are unrelated. At masses lower than ~10^{11} M_sol, quiescent galaxies show a large range in axial ratios, implying a mix of bulge- and disk-dominated galaxies. Our result strongly suggests that major merging is the most important, and perhaps only relevant, evolutionary channel to produce massive (>10^{11} M_sol), quiescent galaxies, as it inevitably results in spheroids.Comment: Minor changes to match published version in ApJ Letter

Mapping low-latitude stellar substructure with SEGUE photometry

Encircling the Milky Way at low latitudes, the Low Latitude Stream is a large stellar structure, the origin of which is as yet unknown. As part of the SEGUE survey, several photometric scans have been obtained that cross the Galactic plane, spread over a longitude range of 50 to 203 degrees. These data allow a systematic study of the structure of the Galaxy at low latitudes, where the Low Latitude Stream resides. We apply colour-magnitude diagram fitting techniques to map the stellar (sub)structure in these regions, enabling the detection of overdensities with respect to smooth models. These detections can be used to distinguish between different models of the Low Latitude Stream, and help to shed light on the nature of the system.Comment: To appear in the proceedings of IAU Symposium 254 "The Galaxy disk in a cosmological context", Copenhagen, June 200