A Longitudinal Analysis of Entries and Exits of the Low-Income Elderly to and from the Supplemental Security Income Program

This paper is the first to analyze eligibility and participation spells and estimate dynamic models of SSI participation by the aged. We first describe eligibility and participation spells and estimate competing-risk models of the determinants of transitions. Next, we present evidence of extensive measurement error in the expected SSI benefit and the associated imputed eligibility status of sample members. We compare and contrast two approaches to ameliorating this error. A cross-section approach exploits self-reports of participants’ benefits, and a longitudinal approach makes inferences from time variation in the computed benefit. We find that the hazard model estimates vary little with regard to whether or which particular measurement error correction is employed. Finally, the longitudinal patterns of eligibility and participation suggest that take-up rates among the persistently eligible are nearly 80 percent.

Public Health Insurance and SSI Program Participation Among the Aged

Previous researchers have noted that the ‘categorical’ Medicaid eligibility accompanying the welfare programs Aid to Families with Dependent Children (AFDC) and Supplemental Security Income (SSI) often far exceeds the value of these programs’ cash benefits. It may be the case that the accompanying health insurance, not the cash benefit, is often the decisive factor in welfare participation. If so, welfare participation should decrease when cash and health insurance benefits are unbundled. We present a simple model of program participation with heterogeneous valuation of health insurance and transaction costs of participation. We evaluate the following four implications of the model: 1) SSI participation declines with the expansion of alternative routes to Medicaid (i.e., noncategorical Medicaid); 2) the availability of noncategorical Medicaid increases Medicaid participation among SSI nonparticipating eligibles; 3) the average SSI benefit collected by welfare recipients is higher when noncategorical Medicaid is available; and 4) the average SSI benefit rejected by nonparticipating SSI eligibles is higher when noncategorical Medicaid is available. Overall, the findings on the model’s testable implications are mixed. The estimates imply strikingly large effects of the presence of alternative routes to Medicaid on both SSI and Medicaid participation, but the results for the hypotheses about SSI benefit amounts are sensitive to controls for recipient characteristics.

SSI for the Aged and the Problem of 'Take-Up'

The Supplemental Security Income (SSI) program provides an income and health care safety net for the elderly poor. The phenomenon of apparently eligible households that do not enroll in, or 'take up' SSI has been noted as a severe problem since the program's inception in 1974. This paper examines SSI eligibility, applications, and participation in the aged population from 1984 (the most recent year analyzed in the literature to date) through 1997. We are fortunate to have administrative data on SSI use that is linked to various panels of the SIPP. We use this information to estimate the SSI-aged application choice. The key findings from the earlier literature are sensitive with respect to exact sample specification, alternative approaches to imputing the expected SSI benefit, and more detailed information on application and receipt culled from administrative files. Our findings suggest that cash benefits may be less influential, and Medicaid access through SSI more influential, than previously estimated.

The Effect of Food Availability on Time and Energy Expenditures of Territorial and Non-Territorial Hummingbirds

We studied the time and energy allocations related to territorial behavior in male Blue-throated Hummingbirds (Lampornis clemenciae; about 8.3 g) under conditions of unlimited and restricted food availability. When food was unlimited. territorial males avoided inter-specific aggression, chasing only 11% of the inter-specific intruders (Black-chinned Hummingbirds, Archilochus alexandri; about 3.5 g). Thus, when food was unlimited, inter-specific intruders were able to forage efficiently, meeting their estimated daily energy requirement with ease (27 kJ/day). Conversely, 81% of intraspecific intruders were chased, and intra-specific intruders were able to feed at territorial feeders only when the territorial male was away. Chases of intra-specific intruders were longer and appeared to be more intense than chases of inter-specific intruders. When food was restricted territorial activity, including the total number of chases engaged in by the territory owner, was significantly reduced, although the basic characteristicso f territorial behavior (e.g., chasesa nd displays) did not change. Territory owners chased a higher proportion of inter-specific intruders when food was restricted (48%), suggestinga n increasei n inter-specific competition. A high proportion of intra-specific competitors continued to be chased (80%), although the total number of intra-specific intruders was lower. We believe that variations in the cost of territoriality are dependent primarily on the level of intra-specific competition. This is supported by the fact that when food was restricted to an amount that could support a maximum of 1.4 L. clemenciae(basedo n doubly labeledw ater measurementso ffield metabolic rate in a previous study), energy intake by the territory owner decreased from 114 kJ/day to 64 Id/day, with the primary difference being number of intra-specific chases. These data also suggest that the exclusion of other hummingbird species might be based strictly on the amount of available food (energy). When food is restricted, inter-specific competition is more costly to the territory owner causing the exclusion of a higher proportion of inter-specific intruders. The high proportion of intra-specific intruders that are chased in either experimental condition suggestst hat territorial behavior in L. clemenciaem ight have functions other than resource protection per se, such as social functions related to their mating system

Implicitly Priming the Social Brain: Failure to Find Neural Effects

Humans have a fundamental need for social relationships. Rejection from social groups is especially detrimental, rendering the ability to detect threats to social relationships and respond in adaptive ways critical. Indeed, previous research has shown that experiencing social rejection alters the processing of subsequent social cues in a variety of socially affiliative and avoidant ways. Because social perception and cognition occurs spontaneously and automatically, detecting threats to social relationships may occur without conscious awareness or control. Here, we investigated the automaticity of social threat detection by examining how implicit primes affect neural responses to social stimuli. However, despite using a well- established implicit priming paradigm and large sample size, we failed to find any evidence that implicit primes induced changes at the neural level. That implicit primes influence behavior has been demonstrated repeatedly and across a variety of domains, and our goal is not to question these effects. Rather, we offer the present study as cautionary evidence that such a paradigm may not be amenable to scanning in an fMRI environment

Are Hummingbirds Facultatively Ammonotelic? Nitrogen Excretion and Requirements as a Function of Body Size

Most birds are uricotelic. An exception to this rule may be nectar-feeding birds, which excrete significant amounts of ammonia under certain conditions. Although ammonia is toxic, because it is highly water soluble its excretion may be facilitated in animals that ingest and excrete large amounts of water. Birdpollinated plants secrete carbohydrate- and water-rich floral nectars that contain exceedingly little protein. Thus, nectarfeeding birds are faced with the dual challenge of meeting nitrogen requirements while disposing of large amounts of water. The peculiar diet of nectar-feeding birds suggests two hypotheses: (1) these birds must have low protein requirements, and (2) when they ingest large quantities of water their primary nitrogen excretion product may be ammonia. To test these hypotheses, we measured maintenance nitrogen requirements (MNR) and total endogenous nitrogen losses (TENL) in three hummingbird species (Archilochus alexandri, Eugenes fulgens, and Lampornis clemenciae) fed on diets with varying sugar, protein, and water content. We also quantified the form in which the by-products of nitrogen metabolism were excreted. The MNR and TENL of the hummingbirds examined were exceptionally low. However, no birds excreted more than 50% of nitrogen as ammonia or more nitrogen as ammonia than urates. Furthermore, ammonia excretion was not influenced by either water or protein intake. The smallest species (A. alexandri) excreted a significantly greater proportion (125%) of their nitrogenous wastes as ammonia than the larger hummingbirds (≈4%). Our results support the hypothesis that nectar-feeding birds have low protein requirements but cast doubt on the notion that they are facultatively ammonotelic. Our data also hint at a possible size-dependent dichotomy in hummingbirds, with higher ammonia excretion in smaller species. Differences in proportionate water loads and/or postrenal modification of urine may explain this dichotomy

Public Health Insurance and SSI Program Participation Among the Aged.

Previous researchers have noted that the ‘categorical’ Medicaid eligibility accompanying the welfare programs Aid to Families with Dependent Children (AFDC) and Supplemental Security Income (SSI) often far exceeds the value of these programs’ cash benefits. It may be the case that the accompanying health insurance, not the cash benefit, is often the decisive factor in welfare participation. If so, welfare participation should decrease when cash and health insurance benefits are unbundled. We present a simple model of program participation with heterogeneous valuation of health insurance and transaction costs of participation. We evaluate the following four implications of the model: 1) SSI participation declines with the expansion of alternative routes to Medicaid (i.e., noncategorical Medicaid); 2) the availability of noncategorical Medicaid increases Medicaid participation among SSI nonparticipating eligibles; 3) the average SSI benefit collected by welfare recipients is higher when noncategorical Medicaid is available; and 4) the average SSI benefit rejected by nonparticipating SSI eligibles is higher when noncategorical Medicaid is available. Overall, the findings on the model’s testable implications are mixed. The estimates imply strikingly large effects of the presence of alternative routes to Medicaid on both SSI and Medicaid participation, but the results for the hypotheses about SSI benefit amounts are sensitive to controls for recipient characteristics.Social Security Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/49423/1/wp117.pd

A Longitudinal Analysis of Entries and Exits of the Low-Income Elderly to and from the Supplemental Security Income Program

This paper is the first to analyze eligibility and participation spells and estimate dynamic models of SSI participation by the aged. We first describe eligibility and participation spells and estimate competing-risk models of the determinants of transitions. Next, we present evidence of extensive measurement error in the expected SSI benefit and the associated imputed eligibility status of sample members. We compare and contrast two approaches to ameliorating this error. A cross-section approach exploits self-reports of participants’ benefits, and a longitudinal approach makes inferences from time variation in the computed benefit. We find that the hazard model estimates vary little with regard to whether or which particular measurement error correction is employed. Finally, the longitudinal patterns of eligibility and participation suggest that take-up rates among the persistently eligible are nearly 80 percent.Social Security Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/57568/1/wp156.pd

Pratylenchus smoliki, a new nematode species (Pratylenchidae: Tylenchomorpha) from the Great Plains region of North America

Pratylenchus smoliki is a new species of root-lesion nematode described from corn-soybean production fields in the Central Great Plains of North America. It is characterized by populations with relatively abundant males, two lip annuli, females with a round functional spermatheca and a conoid to subcylindrical tail with a non-crenate, smooth terminus. In host preference tests, corn and wheat produce the largest nematode populations, whereas sorghum and soybeans produce less than 20% the numbers observed on corn. Scanning electron microscopy reveals that the en face patterns compare to those seen in Pratylenchus pseudocoffeae, P. scribneri, P. hexincisus, and P. alleni. The pattern is described as rectangular to trapezoidal subdorsal and subventral lips adjoining oral disc, but with a clear demarcation between the oral disc and the subdorsal and subventral sectors. A Maximum Likelihood COI tree recognizesP. smoliki as a moderately-well-supported clade with several haplotype subgroups. A Maximum Likelihood partial 28S tree provides strong support for the P. smoliki clade and reinforces the close relationships between species with similar en facepatterns. Topotype specimens of P. alleni were demonstrably different from P. smoliki using DNA markers. The geographic range of P. smoliki overlaps with the ranges of P. alleni, P. scribneri, P. neglectus, P. hexicisus, and P. dakotaensis. The observed host range (corn, rye, sunflower, and wheat) suggests that P. smoliki may be native to the tallgrass prairie region of the Great Plains