Publications des chercheurs de PSE

Ce papier analyse ex-post l'impact de la libéralisation commerciale au Vietnam entre 1993 et 1998, en prenant en considération les différences régionales Premièrement, une analyse du "pass-through" des prix est effectuée pour mesurer comment l'ouverture commerciale a influencé les prix provinciaux. Ces résultats sont alors introduits dans un modèle de ménages agricoles afin de capturer les effets sur les variables ménages telles que les quantités, les revenus et les profits agricoles. Une estimation originale en traitement continu mesure les effets de la libéralisation commerciale proportionnellement à la quantité de culture exportable produite par le ménage. Mes résultats suggèrent que la libéralisation commerciale a affecté les prix domestiques et les variables agricoles différemment selon les groupes de profits et les régions. La libéralisation commerciale dans l'agriculture entre 1993 et 1998 a augmenté les inégalités au Vietnam, avec une évolution négative des profits agricoles pour les plus pauvres.

Western African Sahel faced severe droughts in the 1980s, affecting agricultural production and food security. In recent decades, farmers have faced uncertainty in the timing and amount of rainy seasons and are confronted with erratic rainfall with high interannual variations. Can the experience of past dry events reduce the vulnerability of households to short-term rainfall shocks? In this paper, I match three waves of panel household surveys focusing on agriculture in Nigeria (GHS, from 2010-2016) and high temporal resolution precipitation data set from the Climate Hazard Center (CHIRPS). I show evidence of the extreme importance of the long-dry period of the 1980s and identify more recent droughts in 2013/2015, which are in line with a change in the characteristics of the rainfall trends. Through a two-way-fixed effect strategy, I exploit the spatial variation of the exposition to the 2015 drought. First, I look at the short-term effects of being hit by a drought on agricultural production and food security indicators. I show that being hit by a drought decreases yields by 14%, and decreases the food diversity of households by around 1%. Second, I look at the impacts' heterogeneity according to the plot's experience, using the timing of the year of acquisition of the plot. I compare short-term droughts' effects on households that acquired their first plot before the 1980s dry period to those that acquired it after. Results suggest that acquiring the land before 1985 attenuates the harmful effects of a climate shock, as these particular households have only a 3% reduction in their yields due to the 2015 drought. This is especially the case when households were severely hit in the 1980s. This result might suggest that having a long-lasting experience under extreme dry events on cultivated land reduces vulnerability to rainfall variability.

This paper reviews some of the challenges related to understanding constraints to agricultural productivity improvements in developing countries. It takes a micro-level approach to shed light on the complexity of farmers' adoption of new technologies and practices and of climate change adaptation decisions. The main arguments are illustrated using an example from the evaluation of a randomized pilot program in Nicaragua. The paper also highlights open questions for future research.

La réforme des prestations de sécurité sociale de 1990 a induit, pour les exploitants agricoles, un transfert progressif de l'assiette des cotisations sociales d'une assiette cadastral à une assiette constituée par les revenus professionnels. L'impact de ce changement sur les transitions vers la retraite est a priori ambigu. En effet, selon les niveaux de revenus cadastraux et professionnels, la modification de l'assiette a un effet différent sur le rapport coût sur droits acquis. Une hausse de ce rapport conduit à une augmentation des transitions vers la retraite. Compte tenu de la proportion d'exploitants pour qui la réforme a conduit à une hausse de ce rapport, une des conséquences de cette réforme semble donc avoir été une incitation au départ à la retraite plus précoce. L'absence d'information sur la carrière complète des exploitants agricoles ainsi que la petite taille de notre échantillon ne nous permet toutefois pas de conclure de façon définitive.

This paper discusses the link between trade liberalization and farmers' specialization in exported cash crops. It first estimates how more favorable tariffs abroad on Vietnamese exports in the early 2000's have contributed to an increase in the production of exported cash crops. In order to relate agricultural households' behavior and tariffs abroad on Vietnamese exports, an agricultural trade index is constructed at the province level. This index measures the average tariffs on Vietnamese cash crop exports, applied by Vietnam's trade partners, taking into account each province's natural resources endowment and controlling for endogeneity issues. We then estimate the impact on agricultural production of a variation of the index, using panel data drawn from two household surveys conducted in 2002 and 2004. However, not all agricultural households will gain from export liberalization, it will depend on the specialization.

Empirical analysis of social networks is often based on self-reported links from survey data. How we interpret such data is crucial for drawing correct inference on network effects. We propose a method for testing whether survey responses can safely be interpreted as a link and, if so, whether links are generated by a unilateral or bilateral link formation process. We present two empirical illustrations of the test on risk-sharing links in Tanzania and on communication among Indian farmers, respectively, demonstrating the ability of the methodology to discriminate between competing data-generating processes.

This article analyses the effects of droughts and climate variability on short-term and medium-term adaptation of Colombian rural households. I measure drought in a Differencesin-Differences (DID) framework, as an alternative to the standard approaches decomposing the effects from climate and yearly weather deviations on agricultural productivity and those using the growing degree days and harmful degree days. In the short-term and mediumterm, rural households adapt to the drought of 2010 by increasing the total area planted in crops and livestock, (increasing also the total gross agricultural productivity in value terms) and by working more on the farm. The droughts also increased the use of external sources of water in the farm and made rural households postpone non-housing investments in the farm. I find heterogeneous effects according to the long run mean of temperature in the municipality. Higher temperature affects positively gross agricultural productivity in low-temperature municipalities but negatively high-temperature municipalities. Cereals and coffee seem to benefit from higher temperatures, while vegetables and fruits are more affected.

We examine the effects of a subsidy program in Haiti that provided smallholders subsidies for inputs (rice seeds, fertilizer, pesticides, and specific labor tasks) using a randomized control trial. The program led to lower input use and lower yields in the year subsidies were received, and the decline in input use and yields persisted through the following year. Using data from a complementary information intervention in which randomly selected farmers were provided clarification regarding their future receipt of vouchers, we find evidence suggesting that incorrect expectations of future transfers partially explain the disappointing outcomes. In addition, instead of increasing input use, the subsidies seem to have led farmers to pay off their loans and take fewer new ones. In complex post-emergency environments such as the one in which this program took place, input subsidies may need to be avoided, as they require considerable information to optimally design and careful coordination by many actors to achieve the expected gains.