计量经济分析 = Econometric analysis

We investigate conditions sufficient for identification of average treatment effects using instrumental variables. First we show that the existence of valid instruments is not sufficient to identify any meaningful average treatment effect. We then establish that the combination of an instrument and a condition on the relation between the instrument and the participation status is sufficient for identification of a local average treatment effect for those who can be induced to change their participation status by changing the value of the instrument. Finally we derive the probability limit of the standard IV estimator under these conditions. It is seen to be a weighted average of local average treatment effects.

Evolution and Rationality Some Recent Game-Theoretic Results. Identification and Estimation of Local Average Treatment Effects

Whose Reality Counts?: Putting the first last

The African continent is distinguished by a much higher fertility rate than other regions. Fertility in Africa has remained almost constant at slightly over six children per woman on average while important declines have occurred elsewhere over the past 25 years. High fertility in Africa is often attributed to poor diffusion of family planning early marriage and low female educational attainment but other cultural and economic factors are involved. The significant decline of infant mortality over the past several decades has produced growth rates never before observed. Africas very young populations may be at the origin of uncontrollable political disorder as young persons with bleak prospects fall easy prey to ethnic religious and political extremism. Demographic growth has become an additional barrier to development. High fertility is tolerated or encouraged as constituting a cultural trait but the resulting population growth is not a cultural trait. Demographic pressure has increased environmental problems in many regions. It is estimated that over ten million rural residents of the Sahel have been affected by soil degradation. The per capita availability of arable land fell from one-half to one-third hectare between 1965 and 1987. Shortages of firewood and water have become more common. The relationship between demographic growth environmental crisis and poverty in the countryside depends on other factors such as production techniques modes of access to land and water and the degree of security of land tenure. Population pressure was not the initial factor that disturbed the balance of the traditional societies but it exacerbated the effects of other forces such as the introduction of cash crops and monetarization of the economy. Rural exodus and accelerated urban migration have been prompted in large part by the higher incomes and greater availability of services of all types in the cities. Achieving control of fertility in Africa will require stabilization of rural populations territorial management and reduction of disparities between rural and urban areas.

An end to poverty

Communication for rural innovation: rethinking agricultural extension

Social Capital and Agricultural Innovation in Sub Saharan Africa

Do decentralized innovation systems promote agricultural technology adoption? Experimental evidence from Africa.

Markets have been recognised for their potential to unlock economic growth and development. In the 1980s, there was a widespread promotion of market liberalisation policies across sub-Saharan Africa and other developing regions following the embracing of the market led agricultural development paradigm. Despite decades of promotion of market led development, very few smallholder farmers in SSA participate in commodity markets. The hoped for structural transformation from subsistence to commercial agriculture across SSA remains elusive. The potential of markets as an engine of agricultural growth and a pathway to exit poverty for the majority of the poor smallholder farmers in the region remains not fully exploited. Though a number of studies have attempted to identify market participation factors, none has been extensive in coverage of SSA and has captured effects of the different economic and policy environments. This paper, based on an extensive cross-sectional sample of 6 421 households across eight SSA countries quantifies factors determining participation by smallholder farmers in cereal grain markets. Because of the expected problem of endogeneity between the dependent market participation variable and covariates, the paper adopts the Heckman 2-stage OLS regression model. Variables hypothesised to influence market participation are categorised into: transaction cost, household socioeconomic attributes, biophysical environment (production potential) and public infrastructure and services. The paper draws lessons for policy and development interventions such as IAR4D. Key words: Market participation, Determinants, SSA, Heckman’s procedure, IAR4D

https://learningpublics.org/attachments/article/23/Determinants%20of%20cereal%20market%20participation%20by%20sub-Saharan%20Africa%20smallholder%20farmer.pdf

Determinants of cereal market participation by sub-Saharan Africa smallholder farmer

We use experimental data to investigate whether a decentralised approach to promoting innovation in central African agriculture outperforms conventional extension approaches. Our main result is that this decentralised approach, based on so-called innovation platforms, is effective in reducing poverty - more effective than conventional extension approaches. However, we also document considerable heterogeneity in terms of platform performance.

Decentralised innovation systems and poverty reduction: experimental evidence from Central Africa

In an attempt to enhance agricultural development in sub-Saharan Africa, the region has witnessed an influx of approaches to agricultural technology development and dissemination in the past decades. Yet there is paucity of empirical evidence that links these past approaches to productivity indicators or justify the phasing out of the existing approaches with the new ones. We use cross-sectional baseline data, which were collected in 2008 over 2130 smallholder farmers and 242 villages in East and Central Africa before the implementation of the most recent approach to agricultural research and development known as integrated agricultural research for development (IAR4D), to examine whether the adoption of soil and water conservation technologies (SWCT) generated and disseminated through the past approaches have had an impact on technical efficiency. Taking into account the endogeneity of technology adoption and assuming that impact is heterogeneous across the population, we use an instrumental variable approach to estimate local average treatment effect (LATE). The data suggest that adoption of SWCT has had no significant impact on technical efficiency of smallholder farmers in Rwanda and the Democratic Republic of Congo. However, the impact is negative for smallholder farmers in Uganda as well as for the pooled sample, although the magnitude is small. Thus, the findings justify the need for the introduction of another approach such as IAR4D, which aims at internalising external factors that constrain adoption of improved technologies and technical efficiency.  

	 

	Key words: Impact, adoption, soil and water conservation, technical efficiency, integrated agricultural research for development (IAR4D), local average treatment effect (LATE), Sub-Saharan Africa.

https://www.academicjournals.org/article/article1379952230_Oduol et al.pdf

A.A. Adekunle

Papers

Social Capital and Agricultural Innovation in Sub Saharan Africa

Do decentralized innovation systems promote agricultural technology adoption? Experimental evidence from Africa.

Determinants of cereal market participation by sub-Saharan Africa smallholder farmer

Decentralised innovation systems and poverty reduction: experimental evidence from Central Africa

Impact of adoption of soil and water conservation technologies on technical efficiency: insight from smallholder farmers in sub-Saharan Africa.