The economic consequences of immigration

Available research supports several major conclusions about the economic consequences of immigration. (i) The aggregate impacts of foreign workers on the earnings and employment of native workers are quite small, but differ for selected population subgroups and high ethnic density labor markets. (ii) Immigrants who arrived during the 1970s are less skilled than earlier arrivals, and their earnings will remain substantially below those of natives throughout their working lives. (iii) The evidence on immigrants' receipt of public assistance income is inconclusive.     

The current situation in mexican immigration

By 1988, the Mexican-origin population of the United States had grown to 12.1 million, largely from recent, sharp increases in immigration. The policy concerns raised by this phenomenon have been influenced by some perceptions that available research contradicts. Today most Mexican immigrants come to stay, about half are female, and they have increasingly less schooling compared to the native-born population and other immigrants. Nationally, they do not cause adverse economic effects for native-born workers and, across generations, their language and political assimilation is proceeding well. They put greater demands on education than on other public services. However, the Mexican-origin population affects the economy and public services more and differently in the areas where it is concentrated, primarily in the western United States and large urban areas. Further, the recent legalization of 2.3 million Mexican immigrants can be expected to increase the demand on public services, especially in those areas.     

宋代广南西路的外来移民与地区开发

宋代广南西路人口得到了快速增长,大量外地人因各种原因来此定居,并和当地人一起进行地区开发,从而出现了广西地区开发史上的第一个高峰。但受诸多不利因素的影响,广南西路仍未彻底改变社会经济落后、地广人稀状态。广南西路开发的经验与教训,有助于我们今天揭示人口、资源、环境的协调发展道路。     

宁夏生态移民发展机理与推动机制研究

在国内外学者研究基础上,构建了生态移民区发展机理理论模型,并提出了6条假设;在获取201份有效调研数据后,利用AMOS7.0软件对该理论结构模型进行检验与修正,并最终得到了各变量之间的综合作用程度;最后,有针对性地提出目前少数民族地区生态移民急需建设的四条推动机制:构建合理的生态补偿机制、健全农技推广机制、以产业发展为中心配套可持续发展机制和生产生活与环境融合机制.     

中华绒螯蟹欧洲、美国的移植

中华绒螯蟹(Eriocheir sinensis)属节肢动物门(Arthropoda)、甲壳纲(Crustaceae)、十足目(Decapoda)、方蟹科(Grapsidae)、绒螯蟹属(Eriocheir),自然分布于南至中国福建闽江(～26°N),北至朝鲜半岛(～45°N),西达离长江口约1400km的重庆,由于人为因素,广东珠江流域也有少量存在(图1)。图1为中华绒螯蟹在东亚种群分布状况。中华绒螯蟹原本是东亚的土著生物。但自20世纪初中华绒螯蟹已移居并繁衍于欧美大陆沿海,并在莱茵河河口地区和旧金山湾形成了数量可观的地方群体。图2为中华绒螯蟹在世界范围内的分布情况。     

中华绒螯蟹欧洲、美国的移植

中华绒螯蟹(Eriocheir sinensis)属节肢动物门(Arthropoda)、甲壳纲(Crustaceae)、十足目(Decapoda)、方蟹科(Grapsidae)、绒螯蟹属(Eriocheir),自然分布于南至中国福建闽江(～26°N),北至朝鲜半岛(～45°N),西达离长江口约1400km的重庆,由于人为因素,广东珠江流域也有少量存在(图1)。图1为中华绒螯蟹在东亚种群分布状况。中华绒螯蟹原本是东亚的土著生物。但自20世纪初中华绒螯蟹已移居并繁衍于欧美大陆沿海,并在莱茵河河口地区和旧金山湾形成了数量可观的地方群体。图2为中华绒螯蟹在世界范围内的分布情况。     

科技成果转化和科技有偿服务线路图研究

成果转化是科技与经济结合的关键环节,科技这个第一生产力在促进经济发展中发挥着重要作用。该文通过对科技成果转化和科技有偿服务这两个既相互渗透又相互包容的内涵分析,以农业部南京农业机械化研究所近5年科技成果转化和科技有偿服务情况为例,进行了研究进而探讨了科技成果转化和科技有偿服务的技术线路。     

Scientific Meetings

The 10th International Congress of Entomology will take place in Montreal, 17-25 Aug. 1956. The preliminary announcement that appeared in the 29 July issue failed to mention the year; Science regrets the omission.