Fifty years ago, census microdata were available for only a handful of countries and trans-border access was difficult for all but a few. Now, from www.ipums.org, many decades of census microdata for much of the globe are readily accessible anywhere, free of cost to researchers and students - regardless of country of birth, residence, or citizenship. As of late - 2013, 238 samples representing 74 countries, totaling more than one half billion person records and encompassing more than four fifths of the world's population are available to more than 7,000 registered researchers worldwide. Pioneers of demography developed national and even regional databases for analyzing census microdata (Ruggles 2013), but it is IPUMS that developed the first integrated system for global access. The IPUMS big data revolution, foretold a decade ago (McCaa and Ruggles 2002), has arrived, but is not yet complete. 50 years hence it is likely that almost all census microdata around the globe will be integrated and accessible via multiple systems of access using application programming interfaces (API).The revolution has already sparked much new research. According to a former president of the Population Association of America, students of the Big Census Data Revolution, specifically those with analytical experience using integrated census microdata, enjoy advantages for internships and employment at the World Bank and similar agencies (Meier, Lam, and McCaa 2011). Likewise, Dot-Coms beckon as a new jobs frontier opens for savvy Big Data users (Lohr, 2012:B2).

IPUMS-International disseminates population census microdata at no cost for 69 countries. Currently, a series of 212 samples totaling almost a half billion person records are available to researchers. Registration is required for researchers to gain access to the microdata. Statistics from Google Analytics show that IPUMSInternationals lengthy, probing registration form is an effective deterrent for unqualified applicants. To protect data privacy, we rely principally on sampling, suppression of geographic detail, swapping of records across geographic boundaries, and other minimally harmful methods such as top and bottom coding. We do not use excessively perturbative methods. A recent case of perturbation gone wrong the household samples of the 2000 census of the USA (PUMS), the 20032006 American Community Survey, and the 20042009 Current Population Survey, an empirical study of the impact of perturbation on the usability of UK census microdatathe Individual SARs of the 1991 census of the UK, and a mathematical demonstration in a timely compendium of statistical confidentiality practices confirm the wisdom of IPUMS microdata management protocols and statistical disclosure controls.

Terra Populus, part of NSFs new DataNet initiative, will develop organizational and technical infrastructure to integrate, preserve, and disseminate data describing changes in the human population and environment over time. A plethora of high-quality environmental and population datasets are available, but they are widely dispersed, have incompatible or inadequate metadata, and have incompatible geographic identifiers. The new infrastructure will enable researchers to identify and merge data from heterogeneous sources to study the relationships between human behavior and the natural world. Terra Populus will partner with data archives, data producers, and data users to create a sustainable international organization that will guarantee preservation and access over multiple decades.

An explosion of new data sources describing historical family composition is opening unprecedented opportunities for discovery and analysis. The new data will allow comparative multilevel analysis of spatial patterns and will support studies of the transformation of living arrangements over the past 200 years. Using measurement methods that assess family choices at the individual level and analytic strategies that assess variations across space and time, we can dissect the decline of patriarchal family forms in the developed world and place Northwest Europe and North America in global comparative context.

Many statistical offices recognize the need for enhancing access to census microdata. High costs, challenging risks, and low rewards are substantial obstacles to going-it-alone. An economical, essentially cost-free solution, endorsed by more than 90 National Statistical Offices, is offered by the IPUMS-International project. This paper discusses ten ways the project enhances access and adds value to census microdatagrouped into four categories: 1. statistical confidentiality (security, disclosure protections, managing access), 2. Integration (comprehensive source documentation, integrated metadata, integrated, pooled microdata, IPUMS-I constructed variables), 3. Dissemination (free, trans-border access, custom-tailored extracts), and 4. ethics (statistical transparency, academic freedom, reduction of risks of fraud/mis-representation, and sharing of research findings). Statistical agencies not yet participating in the IPUMS-International initiative are invited to do so. Those already participating are encouraged to entrust 2010 round census microdata to the project in a timely manner.

The Minnesota Population Center (MPC) provides aggregatedata and microdata that have been integrated and harmonized to maximize crosstemporal and cross-spatial comparability. All MPC data products are distributed free of charge through an interactive Web interface that enables users to limit the data and metadata being analyzed to samples and variables of interest to their research. In this article, the authors describe the integrated databases available from the MPC, report on recent additions and enhancements to these data sets, and summarize new online tools and resources that help users to analyze the data over time. They conclude with adescription of the MPCs newest and largest infrastructure project to date: a global population and environment data network.

The Minnesota Population Center (MPC), through the IPUMS-International census microdata project, archives the world's largest stock of census microdata and documentation. A decade of labor assiduously scouring local, national, regional, and international archives on every continent is beginning to bear fruit. Microdata for over 350 censuses for more than 120 countries are safely ensconced in the MPC digital archives. Metadata from more than 900 censuses are catalogued and now being disseminated world-wide without cost in cooperation with National Statistical Institute(NSI) partners and the Integrated Health Survey Network, using the latest international standards for electronic metadata. 5,000 researchers representing more than ninety countries are registered to access confidentialized, integrated microdata without payment and with complete academic freedomthanks to a uniform licensing agreement endorsed by almost one-hundred NSIs. Integration lowers the barriers to entry and facilitates comparative research over space and time.For the future, we plan to integrate and disseminate confidentialized samples of the 2010 round censuses of the sixty-two countries already represented in the database. Samples of an additional 20-30 countries will be released to the global scientific community as time and resources permit. New initiatives are also planned: boundary files for GIS applications, an on-line tabulator forregistered researchers, a secure enclave offering access to full-count microdata at the MPC and perhaps virtual enclaves for partners world-wide with certified secure sites. Several NSI partners have already granted assent for constructing a pilot at the MPC. Before the end of this year, thanks to major funding from the National Science Foundation (USA), a new project, TerraPop, begins--an initiative to combine population microdata with climate and land cover data.

In the last decade, a revolution has occurred in access to census microdata for social and behavioral research. More than 325 million person records (55 countries, 159 samples) representing two-thirds of the worlds population are now readily available to bona fide researchers from the IPUMS-International website: www.ipums.org/international hosted by the Minnesota Population Center. Confidentialized extracts are disseminated on a restricted access basis at no cost to bona fide researchers. Over the next five years, from the microdata already entrusted by National Statistical Office-owners, the database will encompass more than 80 percent of the worlds population (85 countries, ~100 additional datasets) with priority given to samples from the 2010 round of censuses. A profile of the most frequently used samples and variables is described from 64,248 requests for microdata extracts. The development of privacy protection standards by National Statistical Offices, international organizations and academic experts is fundamental to eliciting world-wide cooperation and, thus, to the success of the IPUMS initiative. This paper summarizes the legal, administrative and technical underpinnings of the project, including statistical disclosure controls, as well as the conclusions of a lengthy on-site review by the former Australian Statistician, Mr. Dennis Trewin.

In this article, the authors describe a new data infrastructure project being developed at the Minnesota Population Center. The Integrated Spatio-Temporal Aggregate Data Series (ISTADS) will make it easier for researchers to use publicly available aggregate data for the United States over a time span that covers virtually the entire life of the nation: 17902012. In addition to facilitating access and ease of use, ISTADS will facilitate the use of thesevarious data sets in mapping and spatial analysis.

This study uses a new source of linked census data (N = 6,734) to test theories proposed to explain the high intergenerational coresidence in 19th-century America. Was it a system of support for dependent elderly, or did it reflect intergenerational interdependence? I focus on transitions from middle age to old age, and I assess key predictors of family transitions, including widowhood, retirement, disability, migration, and wealth. The results show that adverse events precipitated changes in the headship of intergenerational families but did not increase the likelihood of residing in an intergenerational family. The findings suggest that 19th-century intergenerational coresidence was not principally a means of old-age support; more often, probably, there was a reciprocal relationship between generations.

In this paper, we investigate the relationship of male and female economic opportunity to marriage formation in 2000, examining how relationships vary with race and ethnicity. To address these issues, we carry out multi-level analysis of the effects of local economic conditions on the marriage decisions of young men and women. We will compare results obtained using the 5% sample of Census 2000 from the Integrated Public Use Microdata Series (IPUMS) with those from an analysis of restricted access census files available only through Census Bureau Research Data Centers (RDCs). The internal files allow the identification of small geographic regions to measure local economic conditions. This analysis will help gauge the value of the restricted access data by presenting a benchmark using public data.

The age of parents at the birth of their children may have profound implications for the subsequent lifecourse of parents, the functioning of the family, and for child health and well-being. Using historicalcensus data from the Integrated Public Use Micro Series, this research explore three dimensions ofparental age: chronological age (Martin et al. 2009), social age (Mare and Tzeng 1989; Eliason et al.2009), and relationship age (Bachu 1999) from the early 1900s until 2008. Little is known about longtermhistorical shifts in these dimensions of age, and to our knowledge, there has been no systematicinvestigation of their interdependence. This research addresses the transformation of family life byinvestigating historical change in three dimensions of parental age and the ways in which thedimensions are woven together.

This note revisits the author's June 2009 PDR article, Reconsidering the Northwest European family system. Using an array of contemporary and historical census microdata from around the world with simple controls for agricultural employment and demographic structure, I detected no significant differences in complex family structure between nineteenth-century Western Europe and North America and twentieth-century developing countries. This article adds two new measures designed to detect stem families and joint families. The results suggest that Western Europeans and North Americans have had a long-standing aversion to joint family living arrangements, and that this pattern cannot be easily ascribed to demographic and economic conditions.

During the past four decades, historians and demographers have argued that historic Northwest Europe and North America had a unique weak family system characterized by neolocal marriage and nuclear family structure. This analysis uses newly available microdata from 97 historical and contemporary censuses of 37 countries to evaluate whether the residential behavior of the aged in historical Northwest Europe and North America was truly distinctive. The results show that with simple controls for agricultural employment and demographic structure, comparable measures of the living arrangements of the aged show little systematic difference between 19th century Northwest Europe and North America and 20th century developing countries. These findings cast doubt on the hypothesis that Northwest Europeans and North Americans had an exceptional historic pattern of preference for nuclear families.

During the past four decades, historians and demographers have argued that historical Northwest Europe and North America had a unique weak-family system characterized by neolocal marriage and nuclear family structure. This analysis uses newly available micro-data from 84 historical and contemporary censuses of 34 countries to evaluate whether the residential behavior of the aged in historical Northwest Europe and North America was truly distinctive. The results show that with simple controls for agricultural employment and demographic structure, comparable measures of the living arrangements of the aged show little systematic difference between nineteenth-century Northwest Europe and North America and twentieth-century developing countries. These findings cast doubt on the hypothesis that Northwest Europeans and North Americans had an exceptional historical pattern of preference for nuclear families.

Virtually all quantitative microdata used by social scientists derive from samples that incorporate clustering, stratification, and weighting adjustments (Kish 1965, 1992). Such data can yield standard error estimates that differ dramatically from those derived from a simple random sample of the same size. Researchers using historical U.S. census microdata, however, usually apply methods designed for simple random samples. The resulting p values and confidence intervals could be inaccurate and could lead to erroneous research conclusions. Because U.S. census microdata samples are among the most widely used sources for social science and policy research, the need for reliable standard error estimation is critical. We evaluate the historical microdata samples of the Integrated Public Use Microdata Series (IPUMS) project from 1850 to 1950 in order to determine (1) the impact of sample design on standard error estimates, and (2) how to apply modern standard error estimation software to historical census samples. We exploit a unique new data source from the 1880 census to validate our methods for standard error estimation, and then we apply this approach to the 18501870 and 19001950 decennial censuses. We conclude that Taylor series estimation can be used effectively with the historical decennial census microdata samples and should be applied in research analyses that have the potential for substantial clustering effects

Newly available census microdata from IPUMS-International are used to assess trends in intergenerational coresidence in 15 developing countries. Contrary to expectations, we find no general decline in intergenerational coresidence over the past several decades. There have been, however, significant changes in the configuration of intergenerational coresidence. Families in which a member of the older generation is household heada configuration consistent with traditional patriarchal forms in which the older generation retains authorityare becoming more common in most of the countries. Intergenerational families headed by a member of the younger generationthe configuration one would expect if intergenerational coresidence were motivated by a need for old-age supportare on the decline in most of the countries. Multivariate analysis reveals that intergenerational families headed by the older generation are positively associated with measures of economic development. These findings are at variance with widely accepted social theory. We hypothesize that housing shortages, economic stress in the younger generation, and old-age pensions may contribute to the change. More broadly, in some developing countries rising incomes may have allowed more people to achieve their preferred family structure of intergenerational coresidence following traditional family forms.