Evaluating the Long-run Impacts of the 9/11 Terrorist Attacks on US Domestic Airline Travel

Although the US airline industry began 2001 with 24 consecutive profitable quarters, including net profits in 2000 totaling $7.9 billion, the impact of the 9/11 event on the industry was substantial. Whereas the recession that began in early 2001 signaled the end of profitability, the 9/11 terrorist attacks pushed the industry into financial crisis after air travel dropped 20% over the September–December 2001 period compared to the same period in 2000. Given the decline in domestic air travel, an important question is whether the detrimental impact of the attacks was temporary or permanent. That is, did airline travel return to the trend that existed prior to the terrorist attacks? There are theoretical reasons to the believe that it would not. Economists have long viewed travel-mode choices as the outcome of a comparison of opportunity costs and benefits. Thus, anything that permanently raises the opportunity cost of travel, holding benefits constant, should reduce the level of travel volume. To determine whether air travel was permanently reduced, we use econometric and time-series forecasting models to generate a counter-factual forecast of air travel volume in the absence of the terrorist attacks. These dynamic forecasts are compared to actual air travel levels to determine the impact of the terrorist attacks. The findings suggest that domestic air travel did not return to the levels that would have existed in the absence of the attack

Evaluating models of climate and forest vegetation

Understanding how the biosphere may respond to increasing trace gas concentrations in the atmosphere requires models that contain vegetation responses to regional climate. Most of the processes ecologists study in forests, including trophic interactions, nutrient cycling, and disturbance regimes, and vital components of the world economy, such as forest products and agriculture, will be influenced in potentially unexpected ways by changing climate. These vegetation changes affect climate in the following ways: changing C, N, and S pools; trace gases; albedo; and water balance. The complexity of the indirect interactions among variables that depend on climate, together with the range of different space/time scales that best describe these processes, make the problems of modeling and prediction enormously difficult. These problems of predicting vegetation response to climate warming and potential ways of testing model predictions are the subjects of this chapter

Poll Workers

Electoral malpractices are commonly thought to occur in polling stations. This chapter makes the normative case for electoral management bodies (EMBs) around the world routinely using poll worker surveys. These surveys provide concrete sources of information about the extent and nature of any problems in the electoral process. Accusations by partisan actors can therefore be readily tested and challenged. Poll worker surveys can therefore increase the transparency of EMBs and the electoral process. They also increase opportunities for evidence based policy making in electoral management. Their usefulness is demonstrated through the first-ever non-US poll worker survey which was undertaken in Britain at the 2015 general election. This survey (n = 1,321) contradicted the existing literature on electoral administration in Britain in a number of ways.</p

So much for #pencilgate: the referendum wasn’t rigged – but Britain’s electoral machinery needs fine-tuning

Despite widespread fears to the contrary, the EU referendum passed off without major problems. But the vote revealed underlying problems with Britain’s electoral system – most notably the difficulty of registering to vote. Toby S James and Alistair Clark, authors of a new report by the Electoral Commission on the quality of electoral administration at the referendum, say the burden on cash-strapped officials is growing. Indeed, nearly half of local authorities say they don’t have enough funding to maintain the electoral register

Expert elicitation of seasonal abundance of North Atlantic right whales Eubalaena glacialis in the mid-Atlantic

This work was supported in part by US Office of Naval Research (ONR) grants to E.F.: N00014-09-1-0896 at University of California, Santa Barbara and N00014-12-1-0274 at University of California, Davis. This work was also supported by ONR grant N000141210286 to the University of St Andrews. In addition, we gratefully acknowledge funding for this work from The Marine Alliance for Science and Technology for Scotland (MASTS). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.North Atlantic right whales (Eubalaena glacialis; henceforth right whales) are among the most endangered large whales. Although protected since 1935, their abundance has remained low. Right whales occupy the Atlantic Ocean from southern Greenland and the Gulf of St. Lawrence south to Florida. The highly industrialized mid-Atlantic region is part of the species’ migratory corridor. Gaps in knowledge of the species’ movements through the mid-Atlantic limit informed management of stressors to the species. To contribute to filling of these gaps, we elicited estimates of the relative abundance of adult right whales in the mid-Atlantic during four months, representing each season, from ten experts. We elicited the minimum, maximum, and mode as the number of individuals in a hypothetical population of 100 right whales, and confidence estimates as percentages. For each month-sex combination, we merged the ten experts’ answers into one distribution. The estimated modes of relative abundances of both sexes were highest in January and April (females, 29 and 59; males, 22 and 23) and lowest in July and October (females, five and nine; males, three and five). In some cases, our elicitation results were consistent with the results of studies based on sightings data. However, these studies generally did not adjust for sampling effort, which was low and likely variable. Our results supplement the results of these studies and will increase the accuracy of priors in complementary Bayesian models of right whale abundances and movements through the mid-Atlantic.Publisher PDFPeer reviewe

Circular avoiding sequences with prescribed sum

AbstractFor given positive integers x, n, and s an x-avoiding circular sequence (of positive integers) of length n and sum s has no set of consecutive terms summing to x, even if wraparound is allowed. A necessary and sufficient condition for the existence of such a sequence is obtained. An effective method to construct avoiding sequences is given. For the cases of most interest the number of avoiding sequences is found