Chest deflection tolerance to blunt anterior loading is sensitive to age but not load distribution

Ninety-three human cadaver tests are used in the development of thoracic injury risk functions with consideration of age and restraint condition. Linear logistic regression models are developed with the set of potential predictors including the maximum chest deflection, the age of the cadaver at death, gender, and the loading condition on the anterior thorax: blunt hub (41 tests), seat belt (26 tests), air bag (12 tests), and combined belt-and-bag (14 tests). Predicted outcomes were the probability of any rib fractures (onset of injury) and the probability of greater than six rib fractures (severe injury). The analysis shows that the injury risk function was not dependent on the loading condition, but was strongly dependent on age. A significant injury risk model with good ability to discriminate injury from non-injury tests (P < 0.0001, chi-square = 21.49, area under receiver operator characteristic curve (ROC) = 0.867, Kruskal's Gamma = 0.732) is presented using only maximum chest deflection and cadaver age as predictors of injury risk. The 50% risk of any rib fractures is found to occur at 35% chest deflection for a 30-year-old, but at 13% deflection for a 70-year-old. The 50% risk of severe injury is shown to occur at 33% chest deflection for a 70-year-old, but at 43% for a 30-year-old.     

When Policies Undo Themselves: Self‐Undermining Feedback as a Source of Policy Change

Most studies of policy feedback have focused on processes of self‐reinforcement through which programs bolster their own bases of political support and endure or expand over time. This article develops a theoretical framework for identifying feedback mechanisms through which policies can become self‐undermining over time, increasing the likelihood of a major change in policy orientation. We conceptualize and illustrate three types of self‐undermining feedback mechanisms that we expect to operate in democratic politics: the emergence of unanticipated losses for mobilized social interests, interactions between strategic elites and loss‐averse voters, and expansions of the menu of policy alternatives. We also advance hypotheses about the conditions under which each mechanism is likeliest to unfold. In illuminating endogenous sources of policy change, the analysis builds on efforts by both historically oriented and rationalist scholars to understand how institutions change and seeks to expand political scientists’ theoretical toolkit for explaining policy development over time.     

Property tax administration in developing countries: Alternatives for land registration and cadastral mapping

The property tax is a widely used fiscal tool in many developing countries. However, property tax evasion and underpayment are common. This fact underscores the need for governments to administer the property tax effectively if they are to maximize revenue for development. A workable system of land registration and cadastral mapping is one of the principal prerequisites for efficient administration of the property tax. This paper examines alternative methods of land registration and cadastral mapping appropriate for governments in developing countries. The registration of deeds and titles is discussed, as are the most appropriate means for their implementation. Similarly, the different types of cadastral systems, fiscal, legal and multi-purpose, and the survey methods necessary for their implementation, are reviewed.