Can sustained economic growth and declining population coexist?

Most of the developed countries have been experiencing sub-replacement fertility. This leads to worries over the sustainability of economic growth in these countries. Given this concern, we ask the following questions: Is there a force that would allow economic growth and declining population to coexist? Is there a mechanism that could reverse the decline in fertility? We argue that returns to human capital in production provide the key to understanding this relation. Our theoretical framework predicts that, when the degree of increasing returns to human capital in traditional production technologies falls, advanced economies switch their productive efforts from labor-oriented technologies that require a constant creation of young workforce toward human capital-oriented technologies that support an ageing population. We call this shift the “endogenous efficiency-augmenting mechanism”. This suggests that sustained economic growth and a declining population can coexist in the long run. Finally, we compare our model against the data and find: (i) The degree of increasing returns to human capital has been falling over time throughout the world along with population growth rates. (ii) Increasing returns to human capital and population growth rates are positively correlated. (iii) Predictions of our model are consistent with what the data reveal.     

Greenhouse gas emissions and mitigation potential from fertilizer manufacture and application in India

Crop management research is increasingly involving farmers in evaluating new technologies, identifying adoption constraints and opportunities for improving farm performance to produce more sustainable impact. ICRISAT and its partners worked with farmers in Malawi and Zimbabwe during the 1999/2000 and 2000/2001 seasons to evaluate a range of ‘best bet’ soil fertility and water management technologies and evaluate the impact of farmer participatory research. Although there was some variation in methods implemented at different sites, the study found that there is a basis for a comparison of methods. Community entry and participatory approaches that engage farmers in decision making throughout the research-development-diffusion-innovation process have higher setup costs compared to traditional ‘top-down’ approaches. But they improve efficiency, both in technology development and in building farmers' capacity for experimentation and collective learning. This results in the development of more relevant technologies, joint learning among farmers, researchers and extensionists and better impact. To make farmer participatory research projects more sustainable and introduce them on a wide scale, the study recommends that public and NGO investments be targeted to building district and village-level innovation clusters.     

Farmer perceptions of legumes and their functions in smallholder farming systems in east Africa

Legumes play an important role in sub-Saharan Africa (SSA) farming systems through the provision of food, feed, fuel, income and a range of biophysical benefits, such as soil fertility enhancement and erosion control. However, their full potential is not being realized. The purpose of this study was to assess farmers’ perceptions and knowledge towards legumes and the rationale of farmers for current legume production practices using a survey of 268 farmers in the Democratic Republic of Congo and Kenya. Most of the farmers had some knowledge of legumes and their characteristics. However, they had little knowledge of some key functions, including soil erosion control and soil fertility improvement. Most farmers relied on radio and other farmers for legume-related information. Farmers with relatively large livestock holdings ranked provision of livestock feed as an important legume function. We conclude that farmers put more value on short-term benefits of legumes including food and income than long-term benefits such as natural resource management and thus grain legumes are more readily identified by farmers than forage species. Also, we conclude that farmers require more than just information about legumes to increase uptake, they also require improved market access to procure inputs and sell products to realize other benefits that are associated with growing legumes.     

Red clover (Trifolium pratense) in conservation agriculture: a compelling case for increased adoption

The rapidly growing population will soon require a near doubling of food production. This increase must be achieved in a manner that maintains environmental integrity, preserves public health and resolves food access and distribution equalities. The use of forage legumes in arable rotations can make significant and multidimensional contributions to this sustainable intensification and this paper reviews the potential contribution of red clover (Trifolium pratense L.), with particular reference to sustainable cereal production in conservation agriculture systems. The use of red clover as a tool in soil fertility-building and the multiple benefits to the cropping system in which it is used is described. The benefits discussed include atmospheric nitrogen fixation, soil conservation, structural soil improvements and a suite of agroecosystem services including increased soil microbial activity, the phytoremediation of polluted soils and the provision of food for pollinators. Reported allelopathic weed suppression by red clover cover crops and the role of modern plant breeding in creating new varieties that further enhance system sustainability is also discussed. Finally, as economic considerations will always impact on adoption rates, the profitability of red clover rotations in terms of silage value and yield benefits is taken into account.     

中国未来生育政策的选择

近年来社会上对是否应该放开中国的计划生育政策有很多争论。争论的起因是由于一些调查数据反映的和某些学者估计出的我国目前生育率非常低;鉴于低生育率已经给比较发达的国家带来了很多问题,所以有人呼吁中国的生育政策应该放开。通过对放开生育政策和不放开生育政策两种情形可能导致的人口学后果进行估计,结合国外的经验和教训,从低生育率的长期后果来分析如何合理地选择生育政策。为了避免人口达到零增长后的快速负增长、快速老龄化和人口规模的迅速减少,国家应该密切关注人们生育意愿的变化,必须在适当的时候放开生育政策,使生育水平保持在2.0左右,从而尽可能地避免长期的、过快的负增长给国家和社会带来更为严重的人口与社会经济问题。     

影响水稻土肥力水平的主要指标筛选

根据对５省２０个水稻土样的测定结果,运用主成分分析的方法,对影响水稻土肥力水平的主要指标进行了筛选,确定出有效铁、有效锰、物理性砂粒、粘粒、细粉粒、田间持水量、脲酶和过氧化氢酶８项指标为影响水稻土肥力水平的主要指标。运用这８项指标可对水稻土的肥力状况进行客观的评价。     

Determinants of Female Fertility in Taiwan, 1966–2001: Empirical Evidence from Cointegration and Variance Decomposition Analysis*

This study investigates the determinants of the fertility rate in Taiwan over the period 1966–2001. Consistent with theory, the key explanatory variables in Taiwan's fertility model are real income, infant mortality rate, female education and female labor force participation rate. The test for cointegration is based on the recently developed bounds testing procedure while the long‐run and short‐run elasticities are based on the autoregressive distributed lag model. Among our key results, female education and female labor force participation rate are found to be the key determinants of fertility in Taiwan in the long run. The variance decom‐position analysis indicates that in the long run approximately 45percent of the variation in fertility is explained by the combined impact of female labor force participation, mortality and income, implying that socioeconomic development played an important role in the fertility transition in Taiwan. This result is consistent with the traditional structural hypothesis.     

人力资本、内生生育行为与经济增长

将生育行为看作内生变量,假定人力资本具有收益递增性,当人力资本存量较多时,孩子质量（人力资本）收益率高于孩子数量收益率,而当人力资本存量较少时,孩子质量收益率低于孩子数量收益率。因此,在人力资本存量较少的社会,家庭选择多生孩子,对每个孩子的人力资本投资较少;而人力资本存量较多的社会,家庭选择少生孩子,对孩子的人力资本投资较多。这导致存在两个稳态均衡,一个是欠发达的具有较多孩子与较少人力资本的稳态均衡,另一个发达的具有较少孩子和较多人力资本的稳态均衡。     

生育和经济社会的协调发展

有三个相关的生育问题需要作些深入研究,第一个是究竞我国当前生育是在什么水平？第二个是假如总和生育率的水平是1．8,这个水平能在今后三十年保持不变吗？第三个是假如未来三十年总和生育率过高或过低于1．8是不是会不利于人口与经济社会的协调发展？第一个问题应该可以用现有的但没有发表的生育数据作更深入分析和举办一次追踪调查去了解妇女生育的历史,追踪同样样本妇女的妊娠结果（活产、死产、流产）和出生儿童的性别。第二个问题的答案是否定的,因为世界上还没有一个国家能够不鼓励生育而能保持正在下降的出生水平。我国社会具备了生育水平继续下降的一切条件,特别是小家庭社会制度的普及更在促进生育水平下降。第三个问题用人口预测的方法比较未来不同生育水平对人口发展的影响,显示出不同预测的人口总数和年龄结构相差不大,无法得出过高和过低于1．8生育水平的未来人口会不利于人口与经济社会的协调发展的结论。