An Analysis of Sample Attrition in Panel Data: The Michigan Panel Study of Income Dynamics

By 1989 the Michigan Panel Study on Income Dynamics (PSID) had experienced approximately 50 percent sample loss from cumulative attrition from its initial 1968 membership. We study the effect of this attrition on the unconditional distributions of several socioeconomic variables and on the estimates of several sets of regression coefficients. We provide a statistical framework for conducting tests for attrition bias that draws a sharp distinction between selection on unobservables and on observables and that shows that weighted least squares can generate consistent parameter estimates when selection is based on observables, even when they are endogenous. Our empirical analysis shows that attrition is highly selective and is concentrated among lower socioeconomic status individuals. We also show that attrition is concentrated among those with more unstable earnings, marriage, and migration histories. Nevertheless, we find that these variables explain very little of the attrition in the sample, and that the selection that occurs is moderated by regression-to-the-mean effects from selection on transitory components that fade over time. Consequently, despite the large amount of attrition, we find no strong evidence that attrition has seriously distorted the representativeness of the PSID through 1989, and considerable evidence that its cross-sectional representativeness has remained roughly intact.

Growth

In nature we see a wide variety of bold colors and unique shapes. Trees personify these characteristics with their curved branches creating distinctive lines and shapes. Leaves and blossoms enhance their structures with an array of colors. Trees possess awe inspiring energy. Each tree is a living thing, its growth shaped by its environment.Similarly, my work is a response to the environment. I employ a spontaneous and bold technique in an attempt to capture the energy I perceive in nature. The use of vigorous lines and high keyed contrasting colors with varied textures conveys that trees are living, growing entities, each one unique. I remain open to new ways of expressing this aesthetic so that my work will continue to grow like a tree and evolve

Do deputy-leaders matter?: a comparative study

Little has been written on deputy-leaders and the received wisdom, such as it is, is that deputy-leaders have little power and hence do not matter. A global survey of deputyleaders found that 68 per cent of states had a deputy-leader. So, however powerful they may be, they are certainly a fairly common political phenomenon. To test whether or not deputy-leaders are politically powerful and thus matter, seven hypotheses were identified with nine observable implications. A comparative approach was adopted, examining the careers of 64 deputy-leaders in five states. The overall results of the tests were somewhat at odds with the perceived wisdom that deputy-leaders do not matter. Furthermore, the outcomes of the tests at the level of the individual states in this study found strong proof that deputy-leaders in the US can influence policy outcomes and there was some proof that British and Swedish deputy-leaders could do so as well

Memo from Peter Fitzgerald to Howard Neville

Memo from Peter Fitzgerald to Howard Neville, January 11, 1974. Raymond H. Fogler Library Special Collections.https://digitalcommons.usm.maine.edu/wilde-stein-exhibit-documents/1022/thumbnail.jp

University Gay Rights Organization to Sponsor Conference

Press release about the May Gay Conferencehttps://digitalcommons.usm.maine.edu/wilde-stein-exhibit-documents/1024/thumbnail.jp

The International Contracting Practices Survey Project: an Empirical Study of the Value and Utility of the United Nations Convention On the International Sale Of Goods (Cisg) and the UNIDROIT Principles of International Commercial Contracts to Practitione

In an era of globalization it is perplexing that so many U.S. practitioners, jurists, and legal academics continue to view contract issues as governed exclusively by state common law and the Uniform Commercial Code. In essence, a significant number of lawyers may be defaulting to the wrong law, in the absence of an effective choice of law clause, when trying to determine the rights and responsibilities arising out of international commercial transactions. The object of the International Commercial Contracting Practices Survey Project was to learn more about how and why this occurs