Researchers are combining self-reports from mobile surveys with passive data collection using sensors and apps on smartphones increasingly more often. While smartphones are commonly used in some groups of individuals, smartphone penetration is significantly lower in other groups. In addition, different operating systems (OSs) limit how mobile data…

Global economic transformations have never been as dramatic as in the twentieth century. Most countries have experienced radical changes in the standards of income per capita, technology, fertility, mortality, income inequality and the extent of democracy in the course of the past century. It is the goal of many disciplines--economics, history,…

Some methodological issues in the study of levels of knowledge are reviewed, and needs for further research are explored, drawing on an analysis of 12 studies reported since the late 1970s. In the 12 studies, 16 quantitative experiments were conducted. These were assessed for internal and external validity. Analysis revealed some shortcomings in…

Approximately 6,500 children are enrolled per year in the New York State Experimental Prekindergarten Program (PreK). In 1975-76 a longitudinal study was begun to determine the program's impact on the development of children while enrolled in the program and in the primary grades. Samples from a population of 5,245 four-year-old prekindergarten…