为都市儿童留出玩乐空间

近来，中心城市儿童在公共空间受到伤亡的报道越来越多。据北京的一次调查表明，“坠楼”是儿童受伤的主要原因，数量甚至多于交通事故。其原由是学校、公园、住宅小区关闭了玩乐场所，交通和停车把儿童从原本属于他们的玩乐空间挤压出去。     

Quality assurance in higher education: analysis of grades for reviewing course levels

In quality assurance, degree courses in European higher education have to demonstrate the course level by means of results. These courses produce many results, among them grades, referring to teachers’ evaluations of students’ performances, and it is our proposal to use them as an effective mean to reflect the course level. Our study examines the criteria that are needed to analyze grades as significant indicators for course levels. We considered what might constitute empirical proof of valid grades and from this analysis we established that the main proof of valid grades consists of measurements of construct validity, scale reliability, intercorrelation and face validity. The analyses delivered insights into the relationship between the proof of valid grades and elements of the curriculum. In the light of these insights we developed four characteristics as reference points for curricula realizing the course level. Following these points, we draw up a procedure to create such curricula. This procedure is explored in a study with eight bachelor degree courses. The conclusion is that the procedure traces the causes of invalid grades and confirms that valid grades are significant indicators of the course level.     

Recent Progress on Endogeneity in Choice Modeling

We describe recent progress in several areas related to endogeneity, including: choice set formation and attention to attributes; interactions among decision-makers; respondents' strategic behavior in answering stated preference choices; models of multiple discrete/continuous choice; distributions of willingness-to-pay; and methods for handling traditionally endogenous explanatory variables.     

Augmenting travel cost models with contingent behavior data

This paper proposes contingent behavior survey questions as a valuable supplement to observed data in travel cost models of non-market demand for recreational resources. A set of observed and contingent behavior results for each survey respondent allows the researcher to control for individual heterogeneity by taking advantage of panel data methods when exploring the nature of respondent demands. The contingent scenarios also provide opportunities to (a) test for differences between observed and contingent preferences and/or (b) assess likely demands under conditionsbeyond the domain of observed variation in costs or resource attributes. Most importantly, contingent scenarios allow the researcher to imposeexogenously varying travel costs. Exogenous imposition of travel costs together with panel methods reduces the omitted variables bias that plagues observed-data travel cost models of recreational demand. Using a convenience sample of data for illustrative purposes, we show how to estimate the demand for recreational angling by combining observed and contingent behavior data. We begin with simple naive pooled Poisson models and progress to more theoretically appropriate fixed effects panel Poisson specifications.The authors are at the University of Nevada and UCLA, respectively. We gratefully acknowledge the comments of both Scott Shonkwiler and participants in the W133 meetings in Santa Fe, New Mexico and for research material provided by Wayne Gray. The data were provided by Rang Narayanan. Research assistance was provided by Jerry McGraw and Natalie Tucker. Research partially supported by the Nevada Experiment Station. Any errors or omissions remain the authors' responsibility.     

Can Stigma Explain Large Property Value Losses? The Psychology and Economics of Superfund

This research documents the long term impacts of delayed cleanup on property values in communities neighboring prominent Superfund sites. The research examines the sale prices of nearly 34,000 homes near sites in three metropolitan areas for up to a 30-year period. To our knowledge, no other property value studies have examined sites in multiple areas with large property value losses over the length of time used here. The results are both surprising and inconsistent with most prior work. The principal result is that, when cleanup is delayed for 10, 15, and even up to 20 years, the discounted present value of the cleanup is mostly lost. A possible explanation for these property value losses is that the sites are stigmatized and the homes in the surrounding communities are shunned. The results suggest that expedited cleanup and minimizing the number of stigmatizing events would reduce these losses. This research was supported by the USEPA under cooperative agreement CR 824393-01-0. The authors wish to thank Alan Carlin for his patience and support along with Shelby Gerking, Kip Viscusi and three anonymous reviewers for their thoughtful comments. We also would like to thank Christian Coerds, Graham Crawford, Rachel Deming, Karen Grace-Martin, Brian Hurd, Joe LaVerde, Eleanor Smith, and Matt Todaro for their support on this project and the participants of the Risk Perception, Valuation and Policy conference at the University of Central Florida and the AERE Workshop in Estes Park, Colorado, for their helpful feedback.     

Popular Support for Climate Change Mitigation: Evidence from a General Population Mail Survey

Using a sample of 1,651 US households, we explore some determinants of willingness to pay (WTP) for climate change mitigation programs. Our mail survey had a relatively low response rate, so we first use several additional data sources to build a detailed sample selection model. This model uses features of the survey instrument, measures of geographic vulnerability to climate change, seasonality, the political mix in the county, attributes of the address or addressee, and a set of factor scores from an extensive factor analysis of all census tracts in the US. We estimate this model jointly with a model to explain climate policy preferences as a function of the domestic and international distribution of policy costs as well as the climate change impacts that each respondent believes will occur under a policy of business-as-usual. Despite statistically significant patterns of nonresponse, selectivity effects are minimal in this case. WTP for climate change mitigation is greater when the domestic incidence of mitigation costs is borne mostly through higher energy taxes. It is also greater when costs are understood to be shared internationally with other groups of countries, rather than being borne mostly by a country group including the US. People are generally more willing to pay for climate change mitigation if they believe that the harm caused by climate change impacts will be substantial, rather than just moderate. The assistance of former UCLA undergraduate students Ivka Adam, Tashi Ghale, Michelle Gogolewski, Vilija Gulbinas, and Lindy Olsson was essential to survey development and administration. This paper is based upon work supported in part by the National Science Foundation under Grant No. 9818875 to UCLA, with additional support from the Raymond F. Mikesell Foundation at the University of Oregon. Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of either the National Science Foundation or ICF International.     

The price of protein: Review of land use and carbon footprints from life cycle assessments of animal food products and their substitutes

Animal husbandry, aquaculture and fishery have major impacts on the environment. In order to identify the range of impacts and the most important factors thereof, as well as to identify what are the main causes of the differences between products, we analysed 52 life cycle assessment studies (LCAs) of animal and vegetal sources of protein. Our analysis was focused only on land requirement and carbon footprints.     

One-stage structural models to explain city size

Several papers have estimated the parameters of Pareto distributions for city sizes in different countries, but only one has attempted to explain the differing magnitudes of these parameters with a set of country-specific explanatory variables. While it is reassuring that there has been some research which advances beyond simple “curve-fitting” to explore the determinants of city size distributions, the existing research uses a two-stage OLS method which yields invalid second-stage standard errors (and, consequently, questionable hypothesis tests). In this paper, we develop candidate one-stage structural models with normal and non-normal errors which accommodate truncated size distributions, potentially Pareto-like shapes, and city-level variables. In general, these new models are nonlinear in parameters. We illustrate with data on U.S. urban areas.     

The Effect of Consumers’ Real-World Choice Sets on Inferences from Stated Preference Surveys

For stated preference (SP) studies, we develop a model that assesses the influence of choice set misspecification arising from the omission of perceived substitutes among real-world alternatives in the same class of goods. This problem is most likely to be present when individuals are allowed to select a “no purchase” option instead of being forced to choose from an explicit set of SP alternatives with hypothetical attribute levels. A convenient feature of our model is that researchers do not need to know exactly which omitted real substitute the individual most prefers, only the set of real substitutes that exists. In our empirical illustration, a comparison of rival models suggests researchers who overlook the presence of perceived real alternatives related to an SP experiment can end up with noticeably biased welfare estimates. Our more-general model suggests that it may be prudent for future SP researchers to anticipate, then test and possibly correct for, distortions in utility parameter estimates that result from this problem.