Empirical Essays on the Economics of Neonatal Intensive Care

The number of neonatal intensive care units (NICUs) in smaller community hospitals increased greatly during the 1980s and 1990s, attracting deliveries away from hospitals with the most sophisticated NICUs. This pattern of ``deregionalization'' has caused concern because previous studies find higher mortality rates for high-risk infants born in hospitals with less sophisticated NICUs relative to those born in hospitals with the highest care level. In this dissertation, I provide causal estimates of the effect of deregionalization on infant health outcomes and treatment intensity. In Chapter 2, I argue that previous estimates of the relationship between the level of care at a high-risk infant's birth hospital and mortality may be biased by unobserved selection. To estimate a causal relationship, I use an instrumental variable strategy that exploits exogenous variation in distance from a mother's residence to hospitals offering each level of care. My instrumental variable estimates are bounded well below ordinary least squares estimates and are not statistically different from zero. These results suggest that relocating patients to hospitals with the highest level of care prior to delivery may not lead to improved mortality outcomes, because infants currently born in lower level facilities have higher unobserved mortality risk. I also provide suggestive evidence that inter-hospital transfer after birth is one mechanism by which infants born at the lowest levels of care achieve similar outcomes to those born at higher level hospitals. In Chapter 3, I test whether additional neonatal intensive care supply leads to excess neonatal intensive care utilization. I exploit within hospital-month variation in the number of vacant NICU beds in an infant's birth hospital the day prior to birth as a source of exogenous variation in supply. I find that the effect of empty beds on NICU admission is positive but very small for the highest risk infants as measured by very low birth weight. However, it is larger for infants with birth weights above this threshold. These results suggest that additional supply of neonatal intensive care resources can lead to increased utilization of intensive care for infants above the very low birth weight threshold

Learning by Doing with Asymmetric Information: Evidence from Prosper.com

Using peer-to-peer (P2P) lending as an example, we show that learning by doing plays an important role in alleviating the information asymmetry between market players. Although the P2P platform (Prosper.com) discloses part of borrowers’ credit histories, lenders face serious information problems because the market is new and subject to adverse selection relative to offline markets. We find that early lenders did not fully understand the market risk but lender learning is effective in reducing the risk over time. As a result, the market excludes more and more sub-prime borrowers and evolves towards the population served by traditional credit markets.

Product Recalls, Imperfect Information, and Spillover Effects: Lessons from the Consumer Response to the 2007 Toy Recalls

In 2007, the Consumer Product Safety Commission (CPSC) issued 276 recalls of toys and other children's products, a sizeable increase from previous years. The overwhelming majority of the 2007 toy recalls were due to high levels of lead content and almost all of these toys were manufactured in China. This period of recalls was characterized by substantial media attention to the issue of consumer product safety and eventually led to the passage of the Consumer Product Safety Improvement Act of 2008. This paper examines consumer demand for toys following this wave of dangerous toy recalls. The data reveal four key findings. First, the types of toys that were involved in recalls in 2007 experienced above average losses in Christmas season sales. Second, Christmas sales of infant/preschool toys produced by manufacturers who did not experience any recalls were about 25 percent lower in 2007 as compared to earlier years, suggesting industry-wide spillovers. Third, a manufacturer’s recall of one type of toy did not lead to a disproportionate loss in sales of their other types of toys. And, finally, recalls of toys that are part of a brand had either positive or negative effects on the demand for other toys in the property, depending on the nature of the toys involved. Our examination of the stock market performance of toy firms over this period also reveals industry wide spillovers. The finding of sizable spillover effects of product recalls to non-recalled products and non-recalled manufacturers has important implications for regulation policy.

Dynamical Constraints on The Masses of the Nuclear Star Cluster and Black Hole in the Late-Type Spiral Galaxy NGC 3621

NGC 3621 is a late-type (Sd) spiral galaxy with an active nucleus, previously detected through mid-infrared [Ne V] line emission. Archival Hubble Space Telescope (HST) images reveal that the galaxy contains a bright and compact nuclear star cluster. We present a new high-resolution optical spectrum of this nuclear cluster, obtained with the ESI Spectrograph at the Keck Observatory. The nucleus has a Seyfert 2 emission-line spectrum at optical wavelengths, supporting the hypothesis that a black hole is present. The line-of-sight stellar velocity dispersion of the cluster is sigma=43+/-3 km/s, one of the largest dispersions measured for any nuclear cluster in a late-type spiral galaxy. Combining this measurement with structural parameters measured from archival HST images, we carry out dynamical modeling based on the Jeans equation for a spherical star cluster containing a central point mass. The maximum black hole mass consistent with the measured stellar velocity dispersion is 3*10^6 solar masses. If the black hole mass is small compared with the cluster's stellar mass, then the dynamical models imply a total stellar mass of ~1*10^7 solar masses, which is consistent with rough estimates of the stellar mass based on photometric measurements from HST images. From structural decomposition of 2MASS images, we find no clear evidence for a bulge in NGC 3621; the galaxy contains at most a very faint and inconspicuous pseudobulge component (M_K>-17.6 mag). NGC 3621 provides one of the best demonstrations that very late-type spirals can host both active nuclei and nuclear star clusters, and that low-mass black holes can occur in disk galaxies even in the absence of a substantial bulge.Comment: 13 pages, 10 figures. Accepted for publication in Ap

Do Social Networks Solve Information Problems for Peer-to-Peer Lending?Evidence from Prosper.com

This paper studies peer-to-peer (p2p) lending on the Internet. Prosper.com, the first p2p lending website in the US, matches individual lenders and borrowers for unsecured consumer loans. Using transaction data from June 1, 2006 to July 31, 2008, we examine what information problems exist on Prosper and whether social networks help alleviate the information problems. As we expect, data identifies three information problems on Prosper.com. First, Prosper lenders face extra adverse selection because they observe categories of credit grades rather than the actual credit scores. This selection is partially offset when Prosper posts more detailed credit information on the website. Second, many Prosper lenders have made mistakes in loan selection but they learn vigorously over time. Third, as Stiglitz and Weiss (1981) predict, a higher interest rate can imply lower rate of return because higher interest attracts lower quality borrowers. Micro-finance theories argue that social networks may identify good risks either because friends and colleagues observe the intrinsic type of borrowers ex ante or because the monitoring within social networks provides a stronger incentive to pay off loans ex post. We find evidence both for and against this argument. For example, loans with friend endorsements and friend bids have fewer missed payments and yield significantly higher rates of return than other loans. On the other hand, the estimated returns of group loans are significantly lower than those of non-group loans. That being said, the return gap between group and non-group loans is closing over time. This convergence is partially due to lender learning and partially due to Prosper eliminating group leader rewards which motivated leaders to fund lower quality loans in order to earn the rewards

Pediatric Emergency Care Research Networks: A Research Agenda

BackgroundPediatric emergency care research networks have evolved substantially over the past two decades. Some networks are specialized in specific areas (e.g., sedation, simulation) while others study a variety of medical and traumatic conditions. Given the increased collaboration between pediatric emergency research networks, the logical next step is the development of a research priorities agenda to guide global research in emergency medical services for children (EMSC).ObjectivesAn international group of pediatric emergency network research leaders was assembled to develop a list of research priorities for future collaborative endeavors within and between pediatric emergency research networks.MethodsBefore an in‐person meeting, we used a modified Delphi approach to achieve consensus around pediatric emergency research network topic priorities. Further discussions took place on May 15, 2018, in Indianapolis, Indiana, at the Academic Emergency Medicine (AEM) consensus conference “Aligning the Pediatric Emergency Medicine Research Agenda to Reduce Health Outcome Gaps.” Here, a group of 40 organizers and participants met in a 90‐minute “breakout” session to review and further develop the initial priorities.ResultsWe reached consensus on five clinical research priorities that would benefit from collaboration among the existing and future emergency networks focused on EMSC: sepsis, trauma, respiratory conditions, pharmacology of emergency conditions, and mental health emergencies. Furthermore, we identified nonclinical research priorities categorized under the domains of technology, knowledge translation, and organization/administration of pediatric emergency care.ConclusionThe identification of pediatric emergency care network research priorities within the domains of clinical care, technology, knowledge translation and organization/administration of EMSC will facilitate and help focus collaborative research within and among research networks globally. Engagement of essential stakeholders including EMSC researchers, policy makers, patients, and their caregivers will stimulate advances in the delivery of emergency care to children around the globe.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147119/1/acem13656.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147119/2/acem13656_am.pd

Itsy bitsy topological field theory

We construct an elementary, combinatorial kind of topological quantum field theory, based on curves, surfaces, and orientations. The construction derives from contact invariants in sutured Floer homology and is essentially an elaboration of a TQFT defined by Honda--Kazez--Matic. This topological field theory stores information in binary format on a surface and has "digital" creation and annihilation operators, giving a toy-model embodiment of "it from bit".Comment: 54 pages, 35 figures. Minor edits, extra figures adde

The JCMT Nearby Galaxies Legacy Survey VII: H\alpha{} imaging and massive star formation properties

We present H\alpha{} fluxes, star formation rates (SFRs) and equivalent widths (EWs) for a sample of 156 nearby galaxies observed in the 12CO J=3-2 line as part of the James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey. These are derived from images and values in the literature and from new H\alpha{} images for 72 galaxies which we publish here. We describe the sample, observations and procedures to extract the H\alpha{} fluxes and related quantities. We discuss the SFR properties of our sample and confirm the well-known correlation with galaxy luminosity, albeit with high dispersion. Our SFRs range from 0.1 to 11 Msun yr-1 with a median SFR value for the complete sample of 0.2 Msun yr-1. This median values is somewhat lower than similar published measurements, which we attribute, in part, to our sample being HI-selected and, thus, not biased towards high SFRs as has frequently been the case in previous studies. Additionally, we calculate internal absorptions for the H\alpha{} line, A(H\alpha{}), which are lower than many of those used in previous studies. Our derived EWs, which range from 1 to 880\AA{} with a median value of 27\AA{}, show little dependence with luminosity but rise by a factor of five from early- to late-type galaxies. This paper is the first in a series aimed at comparing SFRs obtained from H\alpha{} imaging of galaxies with information derived from other tracers of star formation and atomic and molecular gas.Comment: Accepted for publication in MNRAS. 47 pages, 18 figure

Caveats for using statistical significance tests in research assessments

This paper raises concerns about the advantages of using statistical significance tests in research assessments as has recently been suggested in the debate about proper normalization procedures for citation indicators. Statistical significance tests are highly controversial and numerous criticisms have been leveled against their use. Based on examples from articles by proponents of the use statistical significance tests in research assessments, we address some of the numerous problems with such tests. The issues specifically discussed are the ritual practice of such tests, their dichotomous application in decision making, the difference between statistical and substantive significance, the implausibility of most null hypotheses, the crucial assumption of randomness, as well as the utility of standard errors and confidence intervals for inferential purposes. We argue that applying statistical significance tests and mechanically adhering to their results is highly problematic and detrimental to critical thinking. We claim that the use of such tests do not provide any advantages in relation to citation indicators, interpretations of them, or the decision making processes based upon them. On the contrary their use may be harmful. Like many other critics, we generally believe that statistical significance tests are over- and misused in the social sciences including scientometrics and we encourage a reform on these matters.Comment: Accepted version for Journal of Informetric

A census of X-ray nuclear activity in nearby galaxies

We have studied the X-ray nuclear activity of 187 nearby (distance < 15 Mpc) galaxies observed with Chandra/ACIS. We found that 86 of them have a point-like X-ray core, consistent with an accreting black hole (BH). We argue that the majority of them are nuclear BHs, rather than X-ray binaries. The fraction of galaxies with an X-ray detected nuclear BH is higher (~60 per cent) for ellipticals and early-type spirals (E to Sb), and lower (~30 per cent) for late-type spirals (Sc to Sm). There is no preferential association of X-ray cores with a large-scale bar; in fact, strongly barred galaxies appear to have slightly lower detection fraction and luminosity for their nuclear X-ray sources, compared with non-barred or weakly barred galaxies of similar Hubble types. The cumulative luminosity distribution of the nuclear sources in the 0.3-8 keV band is a power-law with slope ~-0.5, from ~2 x 10^{38} erg/s to ~10^{42} erg/s. The Eddington ratio is lower for ellipticals (L_{X}/L_{Edd} ~ 10^{-8}) and higher for late-type spirals (up to L_{X}/L_{Edd} ~ 10^{-4}), but in all cases, the accretion rate is low enough to be in the radiatively-inefficient regime. The intrinsic NH is generally low, especially for the less luminous sources: there appear to be no Type-2 nuclear BHs at luminosities <~ 10^{39} erg/s. The lack of a dusty torus or of other sources of intrinsic absorption (e.g., an optically-thick disk wind) may be directly related to the lack of a standard accretion disk around those faint nuclear BHs. The fraction of obscured sources increases with the nuclear BH luminosity: 2/3 of the sources with L_{X} > 10^{40} erg/s have a fitted NH > 10^{22} cm^{-2}. This is contrary to the declining trend of the obscured fraction with increasing luminosities, observed in more luminous AGN and quasars.Comment: 27 pages, 353 kB, accepted by Ap