Three conditions under which experiments and observational studies produce comparable causal estimates: New findings from within‐study comparisons

This paper analyzes 12 recent within‐study comparisons contrasting causal estimates from a randomized experiment with those from an observational study sharing the same treatment group. The aim is to test whether different causal estimates result when a counterfactual group is formed, either with or without random assignment, and when statistical adjustments for selection are made in the group from which random assignment is absent. We identify three studies comparing experiments and regression‐discontinuity (RD) studies. They produce quite comparable causal estimates at points around the RD cutoff. We identify three other studies where the quasi‐experiment involves careful intact group matching on the pretest. Despite the logical possibility of hidden bias in this instance, all three cases also reproduce their experimental estimates, especially if the match is geographically local. We then identify two studies where the treatment and nonrandomized comparison groups manifestly differ at pretest but where the selection process into treatment is completely or very plausibly known. Here too, experimental results are recreated. Two of the remaining studies result in correspondent experimental and nonexperimental results under some circumstances but not others, while two others produce different experimental and nonexperimental estimates, though in each case the observational study was poorly designed and analyzed. Such evidence is more promising than what was achieved in past within‐study comparisons, most involving job training. Reasons for this difference are discussed. © 2008 by the Association for Public Policy Analysis and Management.     

Saving the league: V.K. Wellington Koo, the league of nations and Sino-Japanese conflict, 1931-39

In 1919, VK. Wellington Koo, the most famous Chinese diplomat of the early twentieth century, participated in the creation of the League of Nations at the Paris Peace Conference. Little over a decade later, as Japanese forces expanded into Manchuria and North China, Koo struggled to save the League he had helped found. He argued that inability or refusal to brand Japan as an aggressor would sound the League's death knell. In vain, Koo tried to convince European statesmen that the Far Eastern Crisis was a litmus test of the League's viability as a collective security organization. From 1936 on, League inaction in the face of Japanese, German and Italian expansion left Koo thoroughly disillusioned. The lessons of the League were not forgotten during World War II, when Koo argued that a more effective collective security organization, in the form of the United Nations, be created on a basis similar to Franklin D. Roosevelt's Four Policemen concept.     

Public Perceptions of Benefits from and Worries over Plant‐Made Industrial Products and Plant‐Made Pharmaceuticals: The Influence of Institutional Trust

Although agricultural biotechnology has been a seminal reference point in risk perception studies, public awareness of their exposure to risk deriving from this new technology has been minimal at best. However, recent events indicate there may be growing public concern as new variations of this technology appear. Understanding what drives perceptions of benefits from the third generation of the agricultural biotechnology and what determines public worries are keys for the future of this technology. To this end, this study analyzes survey data from the midsouth region of the United States to construct four separate regression models of perceived benefits from and worries over plant‐made industrial products and plant‐made pharmaceuticals. Findings suggest that while prior experience with and knowledge about agricultural biotechnology has an impact on perceptions of benefits and worries, trust in farmers plays a highly important role in determining perceptions.     

A retrospective study of drugged driving in Norway

The National Institute of Forensic Toxicology, Oslo, receives blood and urine samples from all Norwegian drivers apprehended on suspicion of driving under the influence of alcohol or drugs. In 1983 we received samples from 1446 drug-suspected drivers, out of which 445 underwent toxicological analysis. The drugs found most frequently were tetrahydrocannabinol (THC) (n = 199), diazepam (n = 166) and amphetamine (n = 102). A cautious interpretation of the data indicate that about 200 of the 445 subjects selected for toxicological analysis drove under severe influence of drugs. Because of the high percentage of submitted cases not analysed for drugs, this figure represents a minimum estimate. Compared with the results from 1978, we found a several-fold increase in detections of THC and amphetamine in 1983. The number of diazepam detections did not increase in a similar way, but we estimated that the diazepam detections would have increased 3-fold if we had analysed as frequent for this drug in 1983 as in 1978.