The reporting of statistical significance in scientific journals

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The reporting of statistical significance in scientific journals

Scientific journals in most empirical disciplines have regulations about how authors should report the precision of their estimates of model parameters and other model elements. Some journals that overlap fully or partly with the field of demography demand as a strict prerequisite for publication that a p-value, a confidence interval, or a standard deviation accompany any parameter estimate. I feel that this rule is sometimes applied in an overly mechanical manner. Standard deviations and p-values produced routinely by general-purpose software are taken at face value and included without questioning, and features that have too high a p-value or too large a standard deviation are too easily disregarded as being without interest because they appear not to be statistically significant. In my opinion authors should be discouraged from adhering to this practice, and flexibility rather than rigidity should be encouraged in the reporting of statistical significance. I would also encourage thoughtful rather than mechanical use of p-values, standard deviations, confidence intervals, and the like.statistical significance

Demography, present and future

-demography

Why does Sweden have such high fertility?

By current European standards, Sweden has had a relatively high fertility in recent decades. During the 1980s and 1990s, the annual Total Fertility Rate (TFR) for Sweden undu­lated consid­erably around a level just under 1.8, which is a bit lower than the corresponding level in France and well above the level in West Germany. (In 2004 the Swedish TFR reached 1.76 on an upward trend.) The Swedish com­pleted Cohort Fertility Rate (CFR) was rather constant at 2 for the cohorts that produced children in the same period; for France it stayed around 2.1 while the West-German CFR was lower and de­clined regularly to around 1.6. In this presentation, I describe the back­ground for these develop­ments and explain the unique Swedish undulations.fertility trends, Germany, impacts of family policies, institutional effects, Sweden

Why does Sweden have such high fertility?

By current European standards, Sweden has had a relatively high fertility in recent decades. During the 1980s and 1990s, the annual Total Fertility Rate (TFR) for Sweden undulated considerably around a level just under 1.8, which is a bit lower than the corresponding level in France and well above the level in West Germany. (In 2004 the Swedish TFR reached 1.76 on an upward trend.) The Swedish completed Cohort Fertility Rate (CFR) was rather constant at 2 for the cohorts that produced children in the same period; for France it stayed around 2.1 while the West-German CFR was lower and declined regularly to around 1.6. In this presentation, I describe the background for these developments and explain the unique Swedish undulations. Part of the explanation of the trend and level in Swedish fertility is the extensive battery of public family policies in the country. They reflect the great generosity, high flexibility, and universalistic approach of the whole system, where family policies are coordinated with educational policies and labor-market policies in an effort to promote the status of women and achieve equity for all residents. The state has been engaged in the development of high-quality all-day childcare arrangements available to all children, and has conducted campaigns to influence public attitudes toward a woman-friendly political culture. Reforms have been motivated by gender-equality considerations and by a drive to induce women to participate in the labor force and to induce men into parenting and childrearing. Legal rules are individualistic, as highlighted by the abolishment of the public widow’s pension and by a tax system where income tax is levied from the individual and not from the married couple or the household, as in Germany. Welfare-state benefits are directed similarly to the individual, not to the family. Policies can be said to focus on the equal right of working women to have children rather than of the right of mothers to have a job. There is no inclination in the Swedish system to encourage a mother to stay home and take care of her children; if anything there has been a move toward securing both-parent participation in childrearing.Sweden, fertility

Preface: Childbearing Trends and Policies in Europe

The editors of the present Special Collection of the electronic journal Demographic Research take pleasure in making the Collection available to the research community and the general public. The Collection’s principal focus is the demographic analysis of European fertility trends, their determinants, and public policies modifying childbearing. The collection is the outcome of an international comparative project. It includes nineteen country studies, eight topical overview chapters, and a summary.childbearing, Europe

Overview Chapter 8: The impact of public policies on European fertility

This chapter outlines the positions in the current debate about the possibility of using public policies to influence fertility. We note the polarization between, on the one hand, those who view public policies as obvious means for lifting the currently low fertility levels in Europe, in line with the role of economic policies in a modern society; and, on the other hand, those who feel that family policies are inefficient, and perhaps even unnecessary. We place the contributions of the national chapters of this book in this framework and describe the formidable methodological difficulties that face those who seek to investigate policy impacts on fertility behavior. While properly conducted empirical investigations have overcome such problems and have clearly demonstrated policy effects in specific circumstances, we conclude that, in general, national fertility is possibly best seen as a systemic outcome that depends more on broader attributes, such as the degree of family-friendliness of a society, and less on the presence and detailed construction of monetary benefits.childbearing, Europe, fertility, public policy

Early traces of the Second Demographic Transition in Bulgaria: a joint analysis of marital and non-marital union formation

In this paper, we study entry into the first conjugal union among young women in Bulgaria in 1980 through 2004 based on data from the national Gender and Generations Survey conducted in 2004. We use an extension of piecewise-constant hazard regression to analyze jointly the transition into a cohabitational union and directly into marriage. This extension will allow us to compare the relative risks of covariates across the two competing transitions, a comparison which infeasible otherwise. In this manner we find, among many other things, that women in the Roma sub-population have more than twice as high a tendency to start a cohabitation as to start a marriage at each age, ceteris paribus, while for ethnic Bulgarian women the relationship is more like 1.5. We also find that a pregnancy leads to a dramatic increase in the rate of both kinds of union formation; the increase is by a factor of over 20 for marriage formation and “only” a factor of around 10 for entry into cohabitation, again ceteris paribus. The standardized marriage intensity for non-pregnant women without children has fallen strongly by a factor of more than six over the period of investigation; the standardized rate of cohabitation has been much more stable and has only fallen by some forty percent, mostly toward the end of the period. These features have not appeared in previous analyses.Bulgaria

Marriage formation as a process intermediary between migration and childbearing

In studies of differences in fertility between migrants and non-migrants, marriage interferes because migration can be motivated by an impending marriage or can entail entry into a marriage market with new opportunities. One would therefore expect elevated fertility after migration, although a competing theory states that on the contrary fertility ought to be reduced in the time around the move because migration temporarily disturbs the life of the migrant. In any case marriage appears as a process that is intermediary between migration and childbearing. To handle such issues it pays to have a technique that allows the analyst to separate any disruptive effects of migration from any boosting effects of marriage in studies of childbearing. The purposes of the present paper is (i) to remind us that such a technique is available, in fact is straightforward, and (ii) to apply the technique to further analyze a set of data on migration and first-time parenthood in Kyrgyzstan recently used by the second author and Gunnar Andersson. The technique has the neat feature that it allows us to operate with several “clocks” at the same time. In the analysis of first births we keep track of time since migration (for migrants) and time since marriage formation (for the married) beside the respondent’s age (for women at childbearing ages); in other connections there may be more clocks. For such analyses we make use of a flexible graphical housekeeping device that allows the analyst to keep track of a feature like whether migration occurs before or after marriage, or at the same time. This is a half-century-old flow chart of statuses and transitions and is not much more complex that the famous Lexis diagram, which originated with Gustav Zeuner, as we now know. These reflexions were first presented at a symposium dedicated to Professor Zeuner.

Childbearing patterns for Swedish mothers of twins, 1961-1999

The Nordic population registers provide a unique possibility to study the demographic behavior of very small population groups and rare events. In this paper, we study the childbearing behavior of Swedish mothers of twins between 1961 and 1999, inclusive. Our most consistent finding is that mothers of twins wait noticeably longer than women with singletons before they have another child. This apart, mothers with twins at their first birth have next-birth fertility patterns very similar to women who have two singletons at their first two births. This commonality in child-bearing behavior does not extend to higher-order births. For mothers with a singleton and a pair of twins, the progression to a third birth depends very much on whether the twins came first or second. Beside these main results our fascinating material also provides a number of descriptive findings. The Swedish twinning rate has increased since the mid-1970s in response to a growing use of fertility-stimulating treatments such as in-vitro fertilization, in parallel with similar developments in many other countries. Such medical procedures are applied mainly to women beyond prime childbearing ages. Nevertheless, we find no simple age pattern in twinning rates. Even in recent years they do not just in-crease with the woman’s age. By way of contrast, at parities beyond 3 twinning rates increase with parity when we control for calendar period, time since last previous birth, and (NB) the woman’s own age.Sweden, twin studies