趋同的城乡生育意愿对生育政策调整的启示--基于北京市城乡独生子女生育意愿的比较研究

对北京市2006年和2008年的城乡独生子女生育意愿作了调查。在我国经济社会较为发达地区,城乡独生子女的生育意愿无论在生育数量还是在子女性别偏好和生育时间上都存在趋同的现象。对目前各省市在生育政策调整时城市和农村依然采取不同政策的做法提出看法。在经济社会较为发达的省市,可以推行城乡一体化的生育政策。     

关于低生育率的理论综述

世界上很多国家已经进入很低生育率行列,中国的部分特大城市甚至已经进入超低生育率。低生育率事实呼唤低生育率理论。对与低生育率相关的七种理论进行分析,包括人口转变理论、理论选择理论、班加茨的低生育率模型、低生育率陷阱理论、扩散理论、性别均衡理论和文化视角。这些理论和模型从人口学、经济学、社会学、女性学、行为主义和文化等不同学科,从宏观、中观和微观等不同层面对生育率进行解读。人口学家不能依靠一个囊括所有方面的宏大理论来解释多样化的低生育率现实,而要从地区模式来理解发展中国家和发达国家不同的低生育率模式。     

农用地自然质量分等与耕地地力评级结果的对比衔接

研究目的:探寻农用地自然质量分等和耕地地力评级结果间的差异与联系.实现其成果的衔接研究方法:模糊综合指数评判法、聚类分析法、层次分析法、GIS叠加分析法、转移矩阵分析、拟合分析。研究结果:(1)农用地自然质量分等和耕地地力评价结果之间等、级变化差异程度不同,同一评价单元农用地自然质量等较多高于耕地地力评价级;(2)平原区等与级结果的差异程度远大于丘陵区;(3)建立了不同指标区农用地自然质量指数与耕地地力评价指数之间的衔接模型,丘陵区衔接模型的线性相关程度明显高于平原区。研究结论:利用衔接模型,可以在农用地自然质量分等和耕地地力评级结果间进行转换,实现了两者在同一指标区的相互衔接检验和不同指标区之间的统一可比性。     

生育率转变过程中家庭子女性别结构的变化－对人口出生性别比偏高的另一种思考

从新的角度对中国人口出生性别比持续偏高现象的原因与表现进行了分析。指出,人口（生育率下降）与社会（生育中的“性别偏好”）因素均对人口性别结构的变化产生影响。妇女曾生（或存活）子女性别比偏离正常值和具有不同孩子性别组合的家庭分布与构成发生变化,是人口出生性别比失常的另一类“积累性”和“后果性”表现。同时,它们具有方法论意义。     

Design of Digital Agricultural Extension Tools: Perspectives from Extension Agents in Nigeria

Given the marked heterogeneous conditions in smallholder agriculture in Sub-Saharan Africa, there is a growing policy interest in site-specific extension advice and the use of digital extension tools to provide site-specific information. Empirical ex-ante studies on the design of digital extension tools and their use are rare. Using data from a choice experiment in Nigeria, we elicit and analyze the preferences of extension agents for major design features of ICT-enabled decision support tools (DSTs) aimed at site-specific nutrient management extension advice. We estimate different models, including mixed logit, latent class and attribute non-attendance models. We find that extension agents are generally willing to use such DSTs and prefer a DST with a more user-friendly interface that requires less time to generate results. We also find that preferences are heterogeneous: some extension agents care more about the effectiveness-related features of DSTs, such as information accuracy and level of detail, while others prioritise practical features, such as tool platform, language and interface ease-of-use. Recognising and accommodating such preference differences may facilitate the adoption of DSTs by extension agents and thus enhance the scope for such tools to impact the agricultural production decisions of farmers.     

人工神经网络产量定量评价模型在县域耕地地力评价中的应用

以辽宁省彰武县为研究对象,在AHP-模糊评价方法的基础上尝试建立耕地地力的ANN-产量定量评价模型。与传统方法相比,模型不需要确定权重,并且能够反映耕地地力评价的非线性特征,消除了传统方法确定权重时人为因素的影响,增加了评价结果的客观性。通过与传统方法的对比发现,得到了较为一致的评价结果,为耕地地力的定量评价探索了一条新的道路。     

Reduced tillage and nitrogen effects on soil water dynamics and maize (Zea mays L.) yield under semi-arid conditions

Soil water and nutrients are critical drivers of crop production for smallholders of southern Africa. A three-year study was conducted to assess the effect of integrating single and double ploughing, ripping and planting basins with nitrogen fertilizer (0, 10 and 20?kg?N?ha^–1) on soil water dynamics and maize (Zea mays L.) yields. The experimental design was factorial with four tillage methods and three nitrogen levels as treatment factors. The study was conducted under semi-arid conditions of Zimbabwe. Tillage methods had similar soil water patterns in the profile and no tillage?×?N interaction effects were observed on soil water dynamics. Soil water penetrated deeper into the profile under ripper and basin methods than conventionally ploughed treatments. Nitrogen increased maize yields (14–96%) and rainwater-use efficiency (20–92%) regardless of tillage methods and growing season quality. However, more studies are required to explore complementary techniques that can improve rainwater capture and prolong soil water storage, and improve soil fertility.     

Does the Welfare State Destroy the Family? Evidence from OECD Member Countries

We study the effect of the size of the welfare state on demographic trends in OECD member countries. Exploiting exogenous variation in public social spending, due to varying degrees of political fractionalization (i.e., the number of relevant parties involved in the legislative process), we show that an expansion in the welfare state increases fertility, marriage, and divorce rates with a quantitatively stronger effect on the marriage rate. We conclude that the welfare state supports family formation in the aggregate. Further, we find that the welfare state decouples marriage and fertility, and therefore alters the organization of the average family.     

How will fertility imbalances affect the human capital structure in China? Evidence from the National Family Planning and Fertility Health Survey

Using the National Family Planning and Fertility Health Survey of 1997 and 2001, we document the preferred fertility level, the actual fertility level and the imbalance between these two for Chinese women. We further study the associations of these outcomes with human capital structure measured by education levels and try to explore the mechanisms behind these associations. The main finding is that there exists severe fertility imbalance in China, and the direction of imbalance is opposite in urban and rural regions. Education plays an important role in determining such imbalance even taking into account other socioeconomic factors. In addition, we find evidence showing that besides economic factors, institutional factors such as the family planning policy may have contributed to the fertility imbalance and the role of education.