This paper is about the scales at which demographic data are available, and demographic research is conducted, and their implications for understanding the relationship between population and environment. It describes a multi-disciplinary project designed to study the long-term relationship between population, land use, and environment in the U.S. Great Plains. The paper begins with a discussion of the scales at which data are readily available for demographic, agricultural land use, and environmental data for the United States. Some of these data can be obtained at relatively high resolutions, but the lowest common denominator for many of the long term data is the county, a fairly large unit. I then discuss the advantages and disadvantages of the different scales available. The third section of the paper uses county net migration as an example of research that can be done, and the scale at which it is effective. The example shows that the county is an effective unit for the study of migration, and that the research results are significant. The conclusion suggests that the study of population processes in an environmental and economic context is appropriate at the county level for some questions, but that scaling the results to larger units may be difficult because of the need to be certain about the contexts in which those processes take place. We probably should not study net migration at the national or continental scale, but aggregating county-level or regional studies to a larger scale may be successful.

Current estimates of long trends in the distribution of personal wealth in the United States combine a number of different studies. However, the trend estimates are open to challenge because of differences in methods of estimation between individual studies. In this article, a sample set from the 1860 census is analyzed and the distribution of wealth among different subsets of the population is described. Holding constant the method of estimation, we conclude that the apparent rise in inequality in the United States between 1774 and 1860, as measured using the Gini coefficient, is overstated by .1.

Nominally free, unrestricted training in portable computer skills is offered by the majority of U.S. temporary help supply (THS) establishments, a practice that is inconsistent with the competitive model of training. This paper asks why temporary help firms provide free general skills training. The answer proposed is that in addition to skills formation, training plays an informational role at THS firms by eliciting private information about worker ability. The model is built on the premise that training is more productive and therefore valuable to high ability workers. Firms offer a package of training and initially lower wages that induces self-selection. Workers of high perceived ability choose training in anticipation of a steeper wage profile while low ability workers are deterred by limited expected gains. Firms profit from their sunk training investment via their short-run informational advantage about ability and thereby limited monopsony power. Market competition among THS firms reduces employer rents, yielding higher wages and more training. Detailed tests of the model using representative establishment data on wages and training find strong support. The analysis demonstrates that beyond providing spot market labor, THS firms gather and sell information about worker quality to clients. The rapid growth of THS as a labor market information broker implies that the demand for worker screening is rising.

During the 1990's the Canadian Families Project (CFP) took random samples of 5% of the 1901 Canadian census and put the information into a computerized database. Because census enumerators used a large number of terms to denote relationships within households and families, it is necessary to develop a common set of numeric codes to define such relationships. The Minnesota Historical Census Project at the University of Minnesota created such codes for the Integrated Public Use Microdata Samples for all US decennial censuses since 1850, and these codes were used for the 1901 Canadian census data. This will facilitate the CFP's study of Canadian family history.

Racial differences in homeownership have long been a topic of sociological study. Previous studies, however, neglected to consider differences in levels of homeownership between nonmarried black and white women in the context of place. Accordingly this paper focuses on the interaction between place, race, and gender and its impact on homeownership for nonmarried persons. The study employs the Integrated Public Use Microdata Series (IPUMS) and logistic regression analysis to address the following questions: Has the racial differential in homeownership for nonmarried women changed from 1970 to 1990? How do place, race, and gender interact to determine the levels of homeownership for nonmarried women? The findings reveal that, although black women were less likely than white women to own homes, the racial differential declined dramatically in rural areas over the two-decade period. The overall trend of decline was opposite to that for urban areas.

The fraction of U.S. college graduate women entering professional programs increased substantially around 1970 and the age at first marriage among all U.S. college graduate women soared just after 1972. We explore the relationship between these two changes and how each was shaped by the diffusion of the birth control pill among young, single college educated women. Although the pill' was approved in 1960 by the FDA and diffused rapidly among married women, it did not diffuse among young single women until the late 1960s when a series of state law changes reduced the age of majority and extended mature minor decisions. We model the impact of the pill on women's careers as consisting of two effects. The pill had a direct positive effect on women's career investment by almost eliminating the chance of becoming pregnant and thus the cost of having sex. The pill also created a social multiplier effect by encouraging the delay of marriage generally and thus increasing a career woman's likelihood of finding an appropriate mate after professional school. We present a collage of evidence pointing to the power of the pill in lowering the costs of long-duration professional education for women. The evidence consists of the striking coincidences in the timing of changes in career investment, marriage age, state laws, and pill use among young single women. The connection between changes in the age at first marriage and the pill is further explored using state variation in laws affecting young single women's pill access. We also evaluate alternative explanations for the changes in career and marriage.

The quantity of machine-readable census material has increased dramatically the last decade. In Britain the 1881 census alone contains over 30 million data records; for Norway both the 1801 and the 1900 censuses are fully transcribed, and in the United States and Canada census-material are now available at the IPUMS and of course the most recent censuses in many countries are held as computer records. Two approaches are usual when working with census material for historical and demographic research: The first uses small subsets of a census with all the original data present and based on the census-lists. The second type of study usually has a greater geographical coverage but use data on aggregate levels and are based on existing published reports. An example of the first approach might be an examination of working class families in part of a town; the second approach might be typified by a be comparative economic history for several towns. The large-scale computerisation of the original census listings change the relationship between these two approaches. In theory; as one has the whole census in machine-readable format, one could consider using the small scale approach on larger (or the whole) scale. It is also quite possible to redo the previously conducted aggregations, and additionally change and make many other and new types of aggregation. This also allows for a much greater freedom in sampling; sampling not rigorously defined by the administrative units of the census. However, in order to use small-scale approaches on larger parts of a census one also needs to computerise the preparation of the source material, i.e. the examination of each record in order to code, classify and/or aggregate for historical analysis. Many of the techniques developed are based on close and individual examination of each individual in the census-lists, like; is this person 'male' or 'female'? What is the relationship to the head of the family, 'son', 'mother in law'? What is the occupation of this individual, and so on. This paper deals with the problems encountered in the formalisation of some types of family and household studies, studies where kin relationship, household composition and household structure are some of the key objects of the study. More specifically the approach for studying family and household developed by the Cambridge Group for the History of Population and Social structure. The group was established in 1964 and the methods and techniques have become quite widespread. This paper seeks to answer two important questions: are these techniques for household studies possible conduct automatically with computer programmes? What processes can be formalised and what are the problems with using computers to do "low-level" interpretations of a historical source.

The Golden Triangle region, located in northwestern Mexico is characterized as a territory that traditionally expels population. During the period 2000-2015, a new variable was added to the factors contributing to the output of its inhabitants: violence, as the result of the strategy implemented by the federal government to combat drug trafficking in 2006-2012. The objective of this research was to determine to what extent unemployment and violence are related to the emigration process. For this, the volume of migrants from the municipalities of the region was analyzed and the main destinations which they relocate were identified. The results showed that there is a relationship between unemployment and emigration and, to a lesser extent, with the gross rate of homicides. Complementarily, key informant and migrants interviews were performed in order to record the perceptions and meanings that individuals give to their mobility experience and the reasons they considered to do it. The findings show two consequences of the same phenomenon: an unplanned that leaves individuals in extreme vulnerability by not having work, housing or resources to support their displacement, and another of those who emigrated for economic reasons and reported not having intentions of returning to their places of origin as does not provide them with equal employment and income opportunities.

Advances in data collection and storage have allowed organizations to create massive, complex and heterogeneous databases, which have stymied traditional methods of data analysis. This has led to the development of new analytical tools that often combine techniques from a variety of fields such as statistics, computer science, and mathematics to extract meaningful knowledge from the data. To support research in this area, UC Irvine has created the UCI Knowledge Discovery in Databases (KDD) Archive (http://kdd.ics.uci.edu) which is a new online archive of large and complex data sets that encompasses a wide variety of data types, analysis tasks, and application areas. This article describes the objectives and philosophy of the UCI KDD Archive. We draw parallels with the development of the UCI Machine Learning Repository and its effect on the Machine Learning community.

The major advances in American life expectancy achieved during the twentieth century began with the remarkable decline in infant mortality between 1910 and 1930. Until the 1990s, explanations of this demographic event centered on improvements in nutrition, public health, and medical science. Recent causal reappraisals emphasize the importance of changes in household-level health behaviors in reducing infant deaths, changes that are consistent with the maternal education campaigns engineered by Progressive Era reformers at the U.S. Children's Bureau. Through qualitative and quantitative analyses of bureau reports and Public Use Micro Sample census data, we link the reformers' philosophy and science to new evidence and conclusions about early improvements in infant survival.