Has Monetary Policy Become More Effective?

Recent research provides evidence of important changes in the U.S. economic environment over the last 40 years. This appears to be associated with an alteration of the monetary transmission mechanism. In this paper we investigate the implications for the evolution of monetary policy effectiveness. Using an identified VAR over the pre- and post-1980 periods we first provide evidence of a reduction in the effect of monetary policy shocks in the latter period. We then present and estimate a fully specified model that replicates well the dynamic response of output, inflation, and the federal funds rate to monetary policy shocks in both periods. Using the estimated structural model, we perform counterfactual experiments to determine the source of the observed change in the monetary transmission mechanism, as well as in the economy's response to supply and demand shocks. The main finding is that monetary policy has been more stabilizing in the recent past, as a result of both the way it has responded to shocks, but also by ruling out non-fundamental fluctuations.

Sticky prices and monetary policy : evidence from disaggregated U.S. data

This paper uses factor-augmented vector autoregressions (FAVAR) estimated using a large data set to disentangle fluctuations in disaggregated consumer and producer prices which are due to macroeconomic factors from those due to sectorial conditions. This allows us to provide consistent estimates of the effects of US monetary policy on disaggregated prices. While sectorial prices respond quickly to sector-specific shocks, we find that for a large number of price series, there is a significant delay in the response of prices to monetary policy shocks. In addition, price responses display little evidence of a “price puzzle,” contrary to existing studies based on traditional VARs. The observed dispersion in the reaction of producer prices is relatively well explained by the degree of market power, as predicted by models with monopolistic competition. JEL Classification: E32, E5

Towards a historical ecology of intertidal foraging in the Mafia Archipelago: archaeomalacology and implications for marine resource management

Understanding the timing and nature of human influence on coastal and island ecosystems is becoming a central concern in archaeological research, particularly when investigated within a historical ecology framework. Unfortunately, the coast and islands of eastern Africa have not figured significantly within this growing body of literature, but are important given their historically contingent environmental, social, and political contexts, as well as the considerable threats now posed to marine ecosystems. Here, we begin developing a longer-term understanding of past marine resource use in the Mafia Archipelago (eastern Africa), an area of high ecological importance containing the Mafia Island Marine Park. Focusing on the comparatively less researched marine invertebrates provides a means for initiating discussion on potential past marine ecosystem structure, human foraging and environmental shifts, and the implications for contemporary marine resource management. The available evidence suggests that human-environment interactions over the last 2000 years were complex and dynamic; however, these data raise more questions than answers regarding the specific drivers of changes observed in the archaeomalacological record. This is encouraging as a baseline investigation and emphasizes the need for further engagement with historical ecology by a range of cognate disciplines to enhance our understanding of these complex issues

On radial limit functions for entire solutions of second order elliptic equations in

Given a homogeneous elliptic partial di®erential operator L of order two with constant complex coe±cients in R2, we consider entire solutions of the equation Lu = 0 for whic

Bone microarchitecture in human foetuses

articleBone microarchitecture is receiving increasing attention in theassessment of the biomechanical properties of bone. While it iswell characterized in normal and pathologic human subjects,few quantitative data are available in human fetal development.In this paper, quantitative parameters of bone microarchitecturein developing human bone are reviewed from the literature andsupplemented by new data from the femoral metaphysis of hu-man fetuses. The samples were imaged using synchrotron radi-ation 3D micro-CT and processed using customized analysismethods. This technique provides 3D model independent mor-phometric parameters, anisotropy, connectivity and geometrycharacteristics, as well as information on mineralization.The morphometric parameters obtained on fetal vertebrae andfemurs evidenced a dense trabecular structure as comparedto that of young adults. The histomorphometric and the 3D mi-cro-CT analysis were consistent to show a significant in-crease of trabecular bone volume with gestational age. Tra-becular bone was found isotropic in vertebral bodies andanisotropic in femoral metaphysis, demonstrating a radialgrowth in vertebrae, and a longitudinal spreading out in longbones such as the femurs. Trabecular thickness in the maturebone of vertebral body and femoral metaphysis was around100 μm, which was in agreement with histomorphometric eval-uation. In the femoral metaphysis, three-dimensional analysisconfirmed the thickening of trabeculae with the distance tothe growth plate, and an estimated rate of thickening around 3μm/day previously obtained in histomorphometry. The 3D net-work was highly connected, and our new geometrical analysistechnique showed a strong prevalence of rod structure ascompared to the plate structure in cancellous bone

Étude expérimentale des transferts d'eau provoqués par l'irrigation sur une parcelle en moyenne vallée du fleuve Sénégal

Alors que l'irrigation paraît être le recours essentiel face aux besoins croissants de la population mondiale en céréales, la dégradation des sols et des eaux annihile presque totalement les efforts d'aménagement. Aussi l'étude de la dégradation des sols dans la moyenne vallée du fleuve Sénégal constitue l'un des quatre objectifs du pôle de recherches sur les systèmes irrigués sahéliens qui regroupe quatre pays dont le Mali, la Mauritanie, le Niger et le Sénégal. Le suivi de l'évolution des eaux et des sols sous culture apparaît indispensable pour garantir une agriculture irriguée rentable et durable dans la zone. Dans cette région, les risques de dégradation des sols font suite à l'effet de deux processus de dégradation que sont l'alcalinisation et la salinisation des sols. Ces types de dégradation sont fortement corrélés à la remontée des nappes d'eaux souterraines. Dans cet article, l'étude des transferts d'eau dans les parcelles irriguées par le biais d'un suivi expérimental " in situ " met en évidence les relations existantes entre les eaux d'irrigation et les mouvements de la nappe. L'étude a permis une meilleure compréhension de la dynamique hydrique au sein de la parcelle : saturation du profil et processus de recharge de la nappe. Elle a également permis de montrer que les échanges avec la nappe pendant la période d'irrigation sont négligeables. Cette pratique de la riziculture inondée, entraîne une variation de stock importante qui représente plus de 40% des apports et qui se traduit par une remontée de nappe de près de 2 mètres.Whereas irrigation appears to be the main approach to satisfy the growing worldwide demand for cereal, soil and water degradation continues to be an on-going problem in agriculture development. One of the main four concerns of the regional group for research on Sahelian irrigated systems (including Mali, Mauritania, Niger and Senegal) is soil degradation in the middle Senegal River valley. These soils are subject to various forms of degradation, mainly from salinisation and/or alkalinisation. These degradation processes are strongly correlated with water table dynamics, with water level fluctuations being significant. Therefore, to guarantee sustainable development of irrigated agriculture in the area, irrigation must be coupled with complete and permanent monitoring of soil and water quality.In this paper, we present a complete study concerning water transfer in irrigated plots and its effects on the groundwater table. The experimental site is located in the Podor region, at 16°.37'N, 14°.52'W in the Donaye irrigated area. The surface area is about 50 ha. Water supply is assured by filling a main channel using a group of pumps on the Doué River. Irrigation of the parcels is performed with siphons from this channel. The experimental plot of 0.33 ha is used for an underwater rice crop. One or two rice crop production harvests are made every year, with the decision been taken by the farmers. There is no drainage system in the area.The experimental plot was equipped with 8 piezometers located along a stream line. One is situated between the plot and the river in order to study the water movements caused by the exchange between the groundwater and the water in the river. Three are situated in the plot, one close to the Doué River, one in the middle of the plot and one near a dam, which is the opposite boundary compared to the river. Four other piezometers are located beyond the dam to estimate groundwater input and output at this boundary. Five tensiometers at 20, 40, 60, 95 and 135 cm depth are placed close to the piezometers located in the plot. Four water content profiles were measured during the irrigation period at depths 20, 40, 60 95 and 135 cm and the irrigation was performed over 84 days.The water table level variations at 2 meters were recorded. The groundwater inflow decreased during the first part of the irrigation period due to infiltration below the irrigated experimental plot. This inflow increased during a second period due to water level variations in the river close to this site. At the output, the head gradient did not vary appreciably and the outflow was assumed to be constant during the observation period. Moreover, this gradient is quite low and the flow rate is very low. The water content and pressure profiles clearly show the infiltration of water in the soil during irrigation. The head gradients show the water movement in the unsaturated soil during infiltration and evaporation. Upward flow due to evaporation is observed at about 10 days after irrigation. The last measured water profile (76 days after the end of irrigation) shows that evaporation modifies the water content profile until at least a depth of 120 cm.The water balance during the irrigation period showed that the input due to irrigation and precipitation was equal to 4150 m3. The evapotranspiration output was estimated to be 2370 m3. Groundwater exchange at the downstream boundary can be neglected during the duration of irrigation (84 days), since the average hydraulic gradient remained low (less than 0.8 %) and the hydraulic conductivity of the aquifer was not important (about 250 cm/day). It was assumed that the water storage quantified with the rise of the groundwater level was equal to the difference between surface input and evapotranspiration (more than 40 % of the contributions), leading to a 27 % change in water content, which is quite reasonable for this type of soil (clay).The stored water was then recovered by evapotranspiration and groundwater outflow at the plot boundaries. We are away from a reasonable irrigation that would reduce the used water quantity and decrease the risk of soil degradation. This study allows a better understanding of the water dynamics in the experimental plot, which includes soil saturation, recharge processes, and exchanges between the aquifer and the river