THE INTERNAL AND EXTERNAL VALIDITY OF THE REGRESSION DISCONTINUITY DESIGN: A META‐ANALYSIS OF 15 WITHIN‐STUDY COMPARISONS

Theory predicts that regression discontinuity (RD) provides valid causal inference at the cutoff score that determines treatment assignment. One purpose of this paper is to test RD's internal validity across 15 studies. Each of them assesses the correspondence between causal estimates from an RD study and a randomized control trial (RCT) when the estimates are made at the same cutoff point where they should not differ asymptotically. However, statistical error, imperfect design implementation, and a plethora of different possible analysis options, mean that they might nonetheless differ. We test whether they do, assuming that the bias potential is greater with RDs than RCTs. A second purpose of this paper is to investigate the external validity of RD by exploring how the size of the bias estimates varies across the 15 studies, for they differ in their settings, interventions, analyses, and implementation details. Both Bayesian and frequentist meta‐analysis methods show that the RD bias is below 0.01 standard deviations on average, indicating RD's high internal validity. When the study‐specific estimates are shrunken to capitalize on the information the other studies provide, all the RD causal estimates fall within 0.07 standard deviations of their RCT counterparts, now indicating high external validity. With unshrunken estimates, the mean RD bias is still essentially zero, but the distribution of RD bias estimates is less tight, especially with smaller samples and when parametric RD analyses are used.     

The Dangers of Relying on a Legal List: A Case Study of the West Virginia Consolidated Investment Fund

Since the mid 1970s, many local governments have begun using state-run local government investment pools for their cash management needs. Some pools operate under statutory limitations on investment instruments known as "legal lists," other pools operate either under a "Prudent Person Rule" standard, while others use a combination of the two. This article examines the potential dangers of an investment pool relying too heavily upon a legal list fiduciary standard, by examining the West Virginia Consolidated Investment Fund, which lost nearly 25 percent of its principal in a financial scandal during the 1980s.     

Investigations into factors affecting the cascade developer used in ESDA--a review

The Electrostatic Detection Apparatus (ESDA) is a technique most commonly used for the visualisation of indented impressions on questioned documents. This work investigates some of the variables which are known to affect the results of ESDA and some variables which have, as yet, not been addressed. The investigation of variables included: examining the effects of different levels of indentation on different qualities of paper, chronological aging of cascade developer and the effects of repeated use of cascade developer on both the quality of results and the glass beads themselves, the effects of storage of cascade developer in a humidified environment and finally the effects of variation on the image development time. Results indicate that chronological aging of cascade developer does not have a negative effect on the quality of results and a 200 g portion of cascade developer will give good quality results for up to 30 traces before the quality will begin to deteriorate. Humidification of the cascade developer appears to have no advantages over storage in a normal environment and, in fact, the toner is lost sooner with humidification. The surface of the glass beads are affected through repeated use of cascade developer and appear to become visually smoother which may lead to a loss of attraction between them and the toner particles.     

The Recent Environmental History of Tiger Leaping Gorge: environmental degradation and local land development in northern Yunnan

Over the past 150 years few Western and Chinese scholars have examined the nature of the environment in Hutiao xia (Tiger Leaping Gorge) and its various inhabitants. However, as a unique geographical and geological feature, one of Asia's deepest gorges, part of the headwaters of the Yangtze River, and a common destination for tourists, the gorge has taken on greater and greater significance. Americans, Chinese literati, Party Cadres, and others have commented on Tiger Leaping Gorge. This essay will examine both the local environment and local environmental practices related to the gorge. Considering historical and contemporary land use practices, the gorge and its changing status can act as a microcosm of western China's various kinds of land development strategies, their implications for local and larger concerns, and land use ideologies of various sorts. Through discussing soil composition, water management, natural vegetation patterns, population growth, and recent developments in tourism, this essay will discuss the human impact on the natural environment of Tiger Leaping Gorge between the 1870s and 2002. It will not only demonstrate patterns in environmental degradation based on both natural and human processes, it will also show that depending on the form of institutional authority and local management practices, the environment in the gorge has been most effected by the political and ideological changes of the last half-century in comparison to earlier times. However, despite increasing challenges in the face of various human factors, some recent environmental practices have succeeded in helping to minimize elements of local soil and vegetation degradation.