探地雷达在公路改扩建工程检测中的应用

公路改扩建工程在广东省正处于快速发展时期,如何准确得到路面病害情况,是旧路处治方案制定面临的主要问题.依托开阳高速改扩建工程,采用三维探地雷达对旧路进行病害检测,得到道路表面及内部的病害分布情况,并分别与人工徒步调查路况及开挖后内部实际情况进行比对.结果表明:当三维探地雷达检测采样间距设置为2.0 cm、驻波时间设置为0.6 ms、时窗设置为85 ns时,可达到较好的检测精准度;三维探地雷达可实现对路面结构内部不同深度位置的裂缝病害进行探测,精确识别3 mm宽裂缝,并了解裂缝的发展方向及性质.     

The effect of education on the minimum wage

This research shows for the first time that the level of education has a causal, negative effect on the minimum wage. I use 2SLS, with historical educational data as an instrument for the level of education in 2010, and I find that across the US states a one percentage point greater proportion of college graduates is associated with a real minimum wage that is lower by 1.5%–1.6%. Also, in order to control for state-level omitted variables, I regress the change in the minimum wage on the change in education and I find again a negative, and significantly at the 1% level, effect. Minimum wage is a policy that is chosen by governments according to voters’ preferences. The results of this research imply that when the level of education increases voters prefer a lower minimum wage.     

Short-time at-the-money skew and rough fractional volatility

The Black–Scholes implied volatility skew at the money of SPX options is known to obey a power law with respect to the time to maturity. We construct a model of the underlying asset price process which is dynamically consistent to the power law. The volatility process of the model is driven by a fractional Brownian motion with Hurst parameter less than half. The fractional Brownian motion is correlated with a Brownian motion which drives the asset price process. We derive an asymptotic expansion of the implied volatility as the time to maturity tends to zero. For this purpose, we introduce a new approach to validate such an expansion, which enables us to treat more general models than in the literature. The local-stochastic volatility model is treated as well under an essentially minimal regularity condition in order to show such a standard model cannot be dynamically consistent to the power law.     

Wish you were here? Quasi-experimental evidence on the effect of education on self-reported attitude toward immigrants

We use European Social Survey and Labour Force Survey data from 2002 to 2012 to estimate the causal effect of years of education on European natives׳ opinion toward immigration, by exploiting the exogenous discontinuity generated by reforms in compulsory education in Europe in the 1940s through the 1990s. Our findings show that higher levels of education lead to a more positive reported attitude toward immigrants. We also investigate the mechanisms behind the effect of education on reported attitudes by evaluating both economic and non-economic channels. We find that higher levels of education place individuals in occupations that are less exposed to the negative effects of migration, although not in sectors/occupations where the share of migrants is necessarily smaller, suggesting that migrants and low-educated natives may be complementary rather than substitutes in the labour market. In addition, education alters values and the cognitive assessment of the role of immigration in host societies, with a positive effect on reported attitude toward diversity and on the assessment of immigration׳s role in host countries. Our findings suggest that education as a policy instrument can increase social cohesion in societies that are subject to large immigration flows.     

The effect of host country Internet infrastructure on foreign expansion of Korean MNCs

This study examines the effect of host country Internet infrastructure on a multinational corporation (MNC) foreign expansion. Using Heckman’s selection model on a sample of 2589 subsidiaries of 487 Korean MNCs between 1990 and 2011, we find that host country Internet infrastructure is important in MNC expansion decisions. In addition, we find that a well-developed Internet infrastructure within a host country leads to more investments from MNCs producing consumer over industrial goods and is more attractive to domestic market followers than market leaders. We find that the host country’s Internet infrastructure is important for an MNC foreign expansion decision, suggesting that efficient communication within an MNC is critical in coordinating globalized MNC subsidiary operations.     

Spatiotemporal dynamics of soybean crop in the Matopiba region,Brazil (1990–2015)

Brazil is a world leader in the production and export of grains, particularly soybeans. The newest agricultural frontier in Brazil is the Matopiba region, which is a continuous zone formed by the states of Maranhão, Tocantins, Piauí, and Bahia, located mostly within the Cerrado biome. The objective of this study was to analyze the spatiotemporal dynamics of soybean production and yield in the Matopiba region. We analyzed municipality-based planted areas and production data obtained by the Brazilian Institute of Geography and Statistics during 1990–2015. Yield was estimated from the production and planted area, and the data were analyzed using global and local Moran indices. The results showed that soybean production in the Matopiba region does not occur randomly. Positive and significant autocorrelation was found at the beginning of the time series among those municipalities located in the west of Bahia. This region influenced the soybean expansion from south to north. Currently, high-production areas are concentrated in two autocorrelated blocks: one in western Bahia and the other in the central Matopiba region. Analysis of spatial autocorrelation involving yield showed a decreasing trend at the end of the time series. The presence of municipalities with high yield surrounded by others with low yield, and vice-versa, were observed. The findings of this study could assist local and regional agricultural planning in the Matopiba region, and support related analyses in other fields of agriculture, the environment, and logistics.     

On the peer effects of star students

We estimate the effect that star students have on their siblings’ learning outcomes, measured by their high school grade point average (GPA) and their math grades. To this end, we couple administrative school data on grades with an unusual natural experiment in Peru that generates exogenous variation in the presence of star students at home. We find that star students increase their siblings’ GPA by 0.33 SDs and their math grades by 0.22 SDs. The effect size is inversely related to number of siblings, suggesting that the remaining siblings act as substitutes for the star student.     

旅游发展对城市工业化的影响及其差异性研究——以58个旅游城市为例

文章构建了旅游业发展影响工业化的理论模型，并利用2000—2016年中国58个旅游城市面板数据和动态面板模型，从总体、专业化、规模和区域等多维度，分析检验了旅游业发展对城市工业化的影响及差异性。结果表明：无论是宏观层面，还是三种分类检验，旅游业发展对城市工业化都具有负向效应。当前，中国旅游城市存在一定的“旅游诅咒”效应，阻滞了其工业化深化；分专业化研究可知，旅游业发展对工业化的负向作用，由大到小依次为旅游高专业化、低专业化和半专业化城市；分规模研究发现，中型旅游城市的最显著，小型旅游城市次之，而大型旅游城市最不显著；分区域研究表明，中西部旅游城市的较突出，而东部旅游城市统计上并不显著。这为各个旅游城市采取有效措施及时防范和规避“旅游诅咒”效应和正确处理“旅游业+工业化”关系提供了参考依据。     

The impact of mandatory trans fat labeling on product mix and consumer choice: A longitudinal analysis of the U.S. Market for margarine and spreads

The impact of changes in food labeling policy on food consumption depends on how market participants—both firms and consumers—react to the changes across all products in the market. We investigate how both responded to the U.S. Food and Drug Administration’s 2006 rule mandating that the quantity of trans fat in food products be separately labeled on the mandatory Nutrition Facts Panel across an entire differentiated product category. Using a longitudinal data set tracking both product offerings and consumer purchases in the market for margarine and spreads for over a decade, we analyze how product mix and consumer purchase behaviors were influenced by the new regulatory requirement. We find that the number of products bearing voluntary “trans fat free” labels increased after the labeling regulation was implemented. However, a large number of the newly introduced products exited the market within five years. As a result, the FDA’s 2006 rule had a stronger short-run than long-run effect on product offerings. Even after the introduction of additional “trans fat free” labeled products, such products remained only a small percentage of margarine and spreads product offerings, increasing from a pre-regulation level of 2.3% of the market to a peak of 6.5% in 2007 before dropping to 3.1% by 2011. In addition to firm response, we examine demand-side reactions to the 2006 rule and find that consumers significantly increased their expenditures on “trans fat free” labeled products soon after the labeling changes were implemented, increasing from about 1.2% of the market in 2001 to a peak of 5.9% in 2007, before returning to 1.8% in 2011. We further explore variations in responses across different demographic characteristics. Although long-run effects are small, the market for “trans fat free” labeled margarine and spreads settled into a new equilibrium with a somewhat higher level of products in the market than prior to the 2006 rule taking effect and a somewhat higher share of expenditures in the category. Overall, our category-wide analysis of both firm and consumer behavior indicates that the effects of the labeling policy change were smaller in the longer run in this market than would be indicated by an analysis of only new product introductions in response to the policy change.     

Fetal Iodine Deficiency and Schooling: A Replication of Field,Robles, and Torero (2009)*

Scholars have theorized that congenital health endowment is an important determinant of economic outcomes later in a person's life. Field, Robles, and Torero (2009, American Economic Journal: Applied Economics 1, 140–169) find large increases in educational attainment caused by a reduction of fetal iodine deficiency following a set of iodine supplementation programs in Tanzania. We revisit the Tanzanian iodine programs with a narrow and wide replication of the study by Field et al. We are able to exactly replicate the original results. We find, however, that the findings are sensitive to alternative specification choices and sample restrictions. We try to address some of these concerns in the wide replication; we increase the sample size fourfold, and we improve the precision of the treatment variable by incorporating new institutional and medical insights. Despite the improvements, no effect is found. We conclude that the available data do not provide sufficient power to detect a possible effect, as treatment assignment cannot be measured with sufficient precision.