Estimating gravity equation models in the presence of sample selection and heteroscedasticity

Gravity models are widely used to explain patterns of trade. However, two stylized features of trade data, sample selection and heteroscedasticity challenge the estimation of gravity models. We propose a two-step method of moments (TS-MM) estimator that deals with both issues. The Monte-Carlo experiments show that the TS-MM estimates are resistant to various combinations of sample selection and heteroscedasticity. Moreover, the TS-MM estimator performs reasonably well even when the data generating process deviates from the TS-MM assumptions. We revisit the world trade in 1990 to illustrate the usefulness of the proposed model, with emphasis on the identification of the extensive margin of trade.     

Rural–urban differences in parental spending on children's primary education in Malawi

Using Malawian data, this paper answers two interrelated questions: are there rural–urban differences in the factors that influence the probability that a household spends or does not spend on own children's education; and are there rural–urban differences in the factors that affect educational expenditure if a household decides to spend? Computed elasticities indicate that spending on education by rural households is more sensitive to changes in income compared with urban households, suggesting that spending on education in rural areas is a luxury good. In both areas, a mother's employment and education has a larger impact on spending compared with those of a father. Urban households compared with their rural counterparts are more sensitive to the quality of access to primary schools. We find no evidence of gender bias in school spending in urban areas, but rural households exhibit bias in favour of boys.     

多传输零点LTCC梳状线带通滤波器的设计与实现

设计了一种改进型的梳状线LTCC滤波器.在一般抽头式梳状线滤波器设计的基础上,结合电路仿真以及三维电磁场仿真,辅之以DOE(design of experiment)的设计方法,设计出一种高抑制、低插损多传输零点的滤波器.滤波器的实际实现采用在当今射频通信器件设计中流行的LTCC技术.该滤波器中心频率为2.45GHz,带宽150MHz,可以广泛运用于无绳电话、蓝牙模块,以及WLAN的射频电路中.     

Protest responses and community attitudes toward accepting compensation to host waste disposal infrastructure

Despite the use of host community compensation to solve NIMBY (Not In My Back Yard) siting difficulties in many industrialised countries, the effectiveness of this policy is still being debated in academic and policy-making arenas. In this paper, we examine attitudes held regarding compensation in communities directly impacted upon by final waste disposal infrastructure projects (landfill and incineration) in Ireland using survey responses to two contingent valuation (CV) scenarios and a question relating to preferences for compensation delivery. We find that communities in the pre-construction planning phase for locally undesirable development are less accepting of compensation offers to host the facility than are communities who have lived with such developments to host an extension to the existing facility in their localities. However, many of our respondents who initially reject compensation offers in the CV question go on to accept at least one compensation package in the later compensation preference question. Using this information allows us to draw a distinction between ‘Hardcore’ and ‘Switcher’ protesters to illustrate a more subtle picture of rejection of locally undesirable facilities and compensation packages than has previously been articulated. Using probit regression analysis, we find that property rights or NIMBY concerns – specifically, the treatment of non-local waste at the facility is a concern for many residents – drive this rejection of compensation. Finally, contrary to previous studies concerning preferences for host compensation, community compensation is not always preferred to individual compensation payments.