Do Children from Welfare Families Obtain Less Education?

This study estimates the relationship between parental welfare receipt and children’s adulthood educational attainment. Data come from the Panel Study of Income Dynamics. Cross-sectional regression results confirm findings from previous studies that greater parental welfare receipt is significantly associated with children’s poorer educational attainment. Fixed-effect regressions indicate that the relationship between parental welfare receipt and children’s educational outcomes becomes weaker after controlling for unobserved family characteristics, but they do not eliminate the negative relationship. The relationship between parental welfare receipt and children’s educational attainment is not uniform across childhood stages. Additional analyses suggest that parental welfare receipt is not negatively related to educational attainment if combined with at least quarter-time work by the mother.

Instrument selection: The case of teenage childbearing and women's educational attainment

Recent research has identified situations in which instrumental variables (IV) estimators are severely biased and has suggested diagnostic tests to identify such situations. We suggest a number of alternative techniques for choosing a set of instruments that satisfy these tests from a universe of a priori plausible candidates, and we apply them to a study of the effects of adolescent childbearing on the educational attainment of young women. We find that substantive results are sensitive to instrument choice, and make two recommendations to the practical researcher: First, it is prudent to begin with a large set of potential instruments, when possible, and pare it down through formal testing rather than to rely on a minimal instrument set justified on a priori grounds. Second, the application of more restrictive tests of instrument validity and relevance can yield results very different from those based on less restrictive tests that produce a more inclusive set of instruments, and is the preferred, conservative approach when improper instrument choice can lead to biased estimates.

How Does Adolescent Fertility Affect the Human Capital and Wages of Young Women?

The consequences of teen childbearing for the future well-being of young women remain controversial. In this paper, we model and estimate the relationship between early childbearing and human capital investment, and its effect on wages in early adulthood. Taking advantage of a large set of potential instruments for fertility—principally state- and county-level indicators of the costs of fertility and fertility control—we use instrumental variables procedures to generate unbiased estimates of the effects of early fertility on education and work experience, and the effects of these outcomes on adult wages. For both black and white women, adolescent fertility substantially reduces years of formal education and teenage work experience. White teenage mothers also obtain less early adult work experience than young women who delay childbearing. We also find that, through these human capital effects, teenage childbearing has a significant effect on a young woman’s market wage at age 25. Our results, unlike those of recent “revisionist” studies, suggest that public policies that reduce teenage childbearing are likely to have positive effects on the economic well-being of many young mothers and their families.

The Twentieth Century Record of Inequality and Poverty in the United States

When the twentieth century is viewed as a whole, no clear trend in income inequality emerges. Inequality was high and rising during the first three decades and peaked during the Depression. It fell sharply during World War II and remained at the lower level in the 1950s and 1960s. From the 1970s through the mid-1990s inequality steadily increased to levels not seen since World War II, though well below those during the first three decades. The rate of poverty exhibited a long-run downward trend from about 60–70 percent in the earlier years of the century to the 12–14 percent range in recent years, with considerable fluctuation around this secular trend. Changes in inequality were produced largely by demographic and technological changes, the growth and decline of various industries, changes in patterns of international trade, cyclical unemployment, and World War II. The primary drivers of the rate of poverty were economic growth and factors that produced changes in income inequality, particularly demographic change and unemployment. Public policy has reduced the market-generated level of inequality, but since 1950 has had little effect on the trend in inequality. Prior to 1950, the growth of government, and particularly the introduction of a broadly based income tax during World War II, coincided with and partly produced the sharp downward shift in inequality of that era. Government had little effect on poverty rates until 1950. Public income transfer programs have reduced poverty rates appreciably in recent decades. Since World War II, when they have been on a large enough scale to matter, changes in tax and transfer policy have tended to reinforce market-generated trends in inequality and poverty rather than offset them.

Universal Formulae for Percolation Thresholds

A power law is postulated for both site and bond percolation thresholds. The formula writes $p_c=p_0[(d-1)(q-1)]^{-a}d^{\ b}$, where $d$ is the space dimension and $q$ the coordination number. All thresholds up to $d\rightarrow \infty$ are found to belong to only three universality classes. For first two classes $b=0$ for site dilution while $b=a$ for bond dilution. The last one associated to high dimensions is characterized by $b=2a-1$ for both sites and bonds. Classes are defined by a set of value for $\{p_0; \ a\}$. Deviations from available numerical estimates at $d \leq 7$ are within $\pm 0.008$ and $\pm 0.0004$ for high dimensional hypercubic expansions at $d \geq 8$. The formula is found to be also valid for Ising critical temperatures.Comment: 11 pages, latex, 3 figures not include

Income redistribution in the European Union

We explore the redistributive effects of taxes and benefits in the 27 member states of the European Union (EU) using EUROMOD, the tax-benefit microsimulation model for the EU. As well as describing redistributive effects in aggregate, we assess and compare the effectiveness of eight individual types of policy in reducing income disparities. We derive results for the 27 members of the EU using policies in effect in 2010 and present them for each country separately as well as for the EU as a whole

The Alvarez impact theory of mass extinction; limits to its applicability and the „great expectations syndrome”

For the past three decades, the Alvarez impact theory of mass extinction, causally related to catastrophic meteorite impacts, has been recurrently applied to multiple extinction boundaries. However, these multidisciplinary research efforts across the globe have been largely unsuccessful to date, with one outstanding exception: the Cretaceous-Paleogene boundary. The unicausal impact scenario as a leading explanation, when applied to the complex fossil record, has resulted in force-fitting of data and interpretations ("great expectations syndrome". The misunderstandings can be grouped at three successive levels of the testing process, and involve the unreflective application of the impact paradigm: (i) factual misidentification, i.e., an erroneous or indefinite recognition of the extraterrestrial record in sedimentological, physical and geochemical contexts, (ii) correlative misinterpretation of the adequately documented impact signals due to their incorrect dating, and (iii) causal overestimation when the proved impact characteristics are doubtful as a sufficient trigger of a contemporaneous global cosmic catastrophe. Examples of uncritical belief in the simple cause-effect scenario for the Frasnian-Famennian, Permian-Triassic, and Triassic-Jurassic (and the Eifelian-Givetian and Paleocene-Eocene as well) global events include mostly item-1 pitfalls (factual misidentification), with Ir enrichments and shocked minerals frequently misidentified. Therefore, these mass extinctions are still at the first test level, and only the F-F extinction is potentially seen in the context of item-2, the interpretative step, because of the possible causative link with the Siljan Ring crater (53 km in diameter). The erratically recognized cratering signature is often marked by large timing and size uncertainties, and item-3, the advanced causal inference, is in fact limited to clustered impacts that clearly predate major mass extinctions. The multi-impact lag-time pattern is particularly clear in the Late Triassic, when the largest (100 km diameter) Manicouagan crater was possibly concurrent with the end-Carnian extinction (or with the late Norian tetrapod turnover on an alternative time scale). The relatively small crater sizes and cratonic (crystalline rock basement) setting of these two craters further suggest the strongly insufficient extraterrestrial trigger of worldwide environmental traumas. However, to discuss the kill potential of impact events in a more robust fashion, their location and timing, vulnerability factors, especially target geology and palaeogeography in the context of associated climate-active volatile fluxes, should to be rigorously assessed. The current lack of conclusive impact evidence synchronous with most mass extinctions may still be somewhat misleading due to the predicted large set of undiscovered craters, particularly in light of the obscured record of oceanic impact events

Exercise and postprandial lipemia: effects on vascular health in inactive adults

Background: There is evidence to suggest that postprandial lipemia are is linked to the impairment of endothelial function, which is characterized by an imbalance between the actions of vasodilators and vasoconstrictors. The aim of this study was to determine the effects of a 12-week high-intensity training (HIT) and moderate continuous training (MCT) protocol on postprandial lipemia, vascular function and arterial stiffness in inactive adults after high-fat meal (HFM) ingestion. Methods: A randomized clinical trial was conducted in 20 healthy, inactive adults (31.6 ± 7.1 years). Participants followed the two exercise protocols for 12 weeks. To induce a state of postprandial lipemia (PPL), all subjects received a HFM. Endothelial function was measured using flow-mediated vasodilation (FMD), normalized brachial artery FMD (nFMD), aortic pulse wave velocity (PWV) and augmentation index (AIx). Plasma total cholesterol, high-density lipoprotein cholesterol (HDL-c), triglycerides and glucose were also measured. Results: The effects of a HFM were evaluated in a fasted state and 60, 120, 180, and 240 min postprandially. A significant decrease in serum glucose between 0 min (fasted state) and 120 min postprandially was found in the HIT group (P= 0. 035). Likewise, FMD (%) was significantly different between the fasted state and 60 min after a HFM in the HIT group (P = 0.042). The total cholesterol response expressed as area under curve (AUC)(0–240) was lower following HIT than following MCT, but no significant differences were observed (8%, P > 0.05). Similarly, triglycerides AUC(0–240) was also lower after HIT compared with MCT, which trended towards significance (24%, P= 0.076). The AUC(0–240) for the glucose response was significantly lower following HIT than MCT (10%, P = 0.008). FMD and nFMD AUC(0–240) were significantly higher following HIT than following MCT (46.9%, P = 0.021 and 67.3%, P = 0.009, respectively). PWV AUC(0–240) did not differ following between the two exercise groups (2.3%, P > 0.05). Conclusions: Supervised exercise training mitigates endothelial dysfunction and glucose response induced by PPL. Exercise intensity plays an important role in these protective effects, and medium-term HIT may be more effective than MCT in reducing postprandial glucose levels and attenuating vascular impairment.This study as funded in part by the Center for Studies on Measurement of Physical Activity, School of Medicine and Health Sciences, Universidad del Rosario (Code N° FIUR DN-BG001). We declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or appropriate data manipulatio