Twinning Rates in Developed Countries: Trends and Explanations

The twinning rate has increased dramatically over the last four decades in developed countries. Two main factors account for this increase: delayed childbearing, as older women tend to have twins more frequently than younger ones, and the expansion of medically assisted reproduction (MAR), which carries an increased probability of multiple births. Using civil registration data, we estimate the share of the increase in twinning rates attributable to the rise in the age at childbearing and to MAR. The effect of MAR is estimated to be about three times as important as the effect of delayed childbearing. Negative health outcomes associated with multiple births and the cost of MAR have raised concerns. We find that in one‐quarter of developed countries with the relevant data, the twinning rate reached a plateau around the early 2000s and decreased thereafter. We examine the reasons for this reversal, in particular changes in MAR policies and practices.     

Beyond tail median and conditional tail expectation: Extreme risk estimation using tail Lp-optimization

The conditional tail expectation (CTE) is an indicator of tail behavior that takes into account both the frequency and magnitude of a tail event. However, the asymptotic normality of its empirical estimator requires that the underlying distribution possess a finite variance; this can be a strong restriction in actuarial and financial applications. A valuable alternative is the median shortfall (MS), although it only gives information about the frequency of a tail event. We construct a class of tail L^p-medians encompassing the MS and CTE. For p in (1,2), a tail L^p-median depends on both the frequency and magnitude of tail events, and its empirical estimator is, within the range of the data, asymptotically normal under a condition weaker than a finite variance. We extrapolate this estimator and another technique to extreme levels using the heavy-tailed framework. The estimators are showcased on a simulation study and on real fire insurance data.     

Physician-sponsored networks. Will physicians take back medicine?

Until about the late 1980s, American physicians and their allies, hospitals and the health care manufacturing industries, dominated all facets of the health system--the clinical, the economic, and the political. The bulk of these providers' revenue flowed to them from a highly fragmented insurance system whose governing principle was to provide each insured patient free choice of doctor and hospital. Two distinct, concurrent shifts threaten to erode the medical profession's traditional dominance. The first is a rapid, general shift of control from the supply side of the health sector to its demand side. The second is a shift away from government control, over which organized medicine held much sway in the past, toward private regulators--the executives of the managed care industry. Is the trend towards greater dependence of practicing physicians on non-physician executives inevitable, or can physicians retain--and, in part, regain--their hitherto autonomous position in the health system?     

Health care futures. Part 2: The future of physician executives? Panel discussion

What is the future of health care in America? This is Part 2 of The Physician Executive panel discussion that explores the future of health care in America. To narrow this ambitious focus somewhat, the future is defined as five to 10 years hence. In Part 1, which was published in the May/June issue, Russell C. Coile, Jr., Barbara LeTourneau, MD, MBA, FACPE, James Reinertsen, MD, Uwe Reinhardt, PhD, Marshall Ruffin, MD, MPH, MBA, FACPE, and David Vogel, MS, shared their opinions about what the future holds in managed care, information technology, and biotechnology. In Part 2, Susan Cejka, Barbara LeTourneau, MD, MBA, FACPE, John Henry Pfifferling, PhD, Uwe Reinhardt, PhD, and James Todd, MD, share their views on the future of medical education and physician executives.     

Impact of physical activity and sedentary behaviour on fall risks in older people: a systematic review and meta-analysis of observational studies

The objective of this work was to summarise and evaluate the evidence showing that physical activity is a protector factor as regards falls in older people. Relevant studies were identified through a systematic search in the MEDLINE and Cochrane Library, under the keywords of accidental fall/numerical data and risk factors, and with the bibliographies of retrieved papers. The combined odds ratio (OR) [95% confidence interval] for physical activity was 0.75 [0.64, 0.88] with moderate heterogeneity (I ²?=?33%). For fall injury, it was 0.59 [0.47, 0.74] and, for falls in general, it rose to 0.94 [0.76, 1.17] with nil heterogeneity. The combined OR for sedentary factors was 1.14 [1.10, 1.82] with moderate heterogeneity (I ²?=?36%). Regular physical activity in daily life yields significant reduction in falls in older people, especially falls with injuries.     

Being the best or doing the right thing? An investigation of positional,prosocial and conformist preferences in provision of public goods

Based on a simple theoretical framework, we show that when individuals exhibit positional, prosocial or conformist preferences which are endogenous, the end outcomes in terms of private provision of public goods can differ significantly from traditional neo-classical predictions. Indeed, when a given individual selects a specific subset of preferences according to what others do, he/she will contribute positively to the public good provision. We provide anecdotal evidence to support our theoretical analysis by using data from an Internet survey on a sample of French individuals. Analyses of individual responses confirm our theoretical arguments. For instance, we show that relative concerns matter, that is, for several environmental goods, people might prefer polluting more in absolute terms but less than others in society. Moreover, we also test whether people exhibit a social desirability bias and show that they attribute more (less) positional (prosocial) concerns to others in society.     

Reporting Errors in Siblings’ Survival Histories and Their Impact on Adult Mortality Estimates: Results From a Record Linkage Study in Senegal

Estimates of adult mortality in countries with limited vital registration (e.g., sub-Saharan Africa) are often derived from information about the survival of a respondent’s siblings. We evaluated the completeness and accuracy of such data through a record linkage study conducted in Bandafassi, located in southeastern Senegal. We linked at the individual level retrospective siblings’ survival histories (SSH) reported by female respondents (n = 268) to prospective mortality data and genealogies collected through a health and demographic surveillance system (HDSS). Respondents often reported inaccurate lists of siblings. Additions to these lists were uncommon, but omissions were frequent: respondents omitted 3.8 % of their live sisters, 9.1 % of their deceased sisters, and 16.6 % of their sisters who had migrated out of the DSS area. Respondents underestimated the age at death of the siblings they reported during the interview, particularly among siblings who had died at older ages (≥45 years). Restricting SSH data to person-years and events having occurred during a recent reference period reduced list errors but not age and date errors. Overall, SSH data led to a 20 % underestimate of ₄₅ q ₁₅ relative to HDSS data. Our study suggests new quality improvement strategies for SSH data and demonstrates the potential use of HDSS data for the validation of “unconventional” demographic techniques.     

Corporate communications managers in large firms: new challenges

The new organisational form of large corporations (horizontal organisation), is affecting the communications job. This corporate transformation leads to new challenges for the corporate communications manager and his team. On the one hand, he has to develop a fully integrated strategy which enables the different forms of communication to contribute to the success of the firm's mission (a common goal). On the other hand, he has to provide small business units, led by strong front-line managers, with professional services. The analysis of several companies will show that the position of the corporate communications department is subject to various pressures and that the development of the `communications function' is calling into question the corporate communications manager's `profession'.