42,982 research outputs found

    Nonparametric causal effects based on incremental propensity score interventions

    Full text link
    Most work in causal inference considers deterministic interventions that set each unit's treatment to some fixed value. However, under positivity violations these interventions can lead to non-identification, inefficiency, and effects with little practical relevance. Further, corresponding effects in longitudinal studies are highly sensitive to the curse of dimensionality, resulting in widespread use of unrealistic parametric models. We propose a novel solution to these problems: incremental interventions that shift propensity score values rather than set treatments to fixed values. Incremental interventions have several crucial advantages. First, they avoid positivity assumptions entirely. Second, they require no parametric assumptions and yet still admit a simple characterization of longitudinal effects, independent of the number of timepoints. For example, they allow longitudinal effects to be visualized with a single curve instead of lists of coefficients. After characterizing these incremental interventions and giving identifying conditions for corresponding effects, we also develop general efficiency theory, propose efficient nonparametric estimators that can attain fast convergence rates even when incorporating flexible machine learning, and propose a bootstrap-based confidence band and simultaneous test of no treatment effect. Finally we explore finite-sample performance via simulation, and apply the methods to study time-varying sociological effects of incarceration on entry into marriage

    Oviposition by \u3ci\u3eDendrosoter Protuberans\u3c/i\u3e (Hymenoptera: Braconidae) on Larvae of \u3ci\u3eScolytus Multistriatus\u3c/i\u3e (Coleoptera: Scolytidae) Occupied by Larvae of \u3ci\u3eEntedon Leucogramma\u3c/i\u3e (Hymenoptera: Eulophidae)

    Get PDF
    Dendrosoter protuberans (Nees) was introduced into the United States from France as a possible addition to the existing spectrum of hymenopterous parasites of the smaller European elm bark beetle, Scolytus multistriarus (Marsham). D. protuberans is an external parasite; it oviposits through bark onto or next to late-instar larvae of S. multistriatus (Kennedy 1970) (Fig. 1)

    Reconsidering the Relationship between the State, Donors, and NGOs in Bangladesh

    Get PDF
    The growth in size and significance of NGOs and particularly of Grameen Bank and the Bangladesh Rural Advancement Committee (BRAC) in Bangladesh challenges the idealtypical relationship between the state, donors and NGOs. Such an ideal envisions a clear demarcation of roles in which NGOs compete with other NGOs for resources from the state and/or donors and one in which NGO activities and programmes are regulated or held accountable by their respective funding sources. The emergence of large multitasking NGOs in a relatively small and weak state such as Bangladesh belies this ideal. Grameen and BRAC compete with government ministries for donor funding; statal institutions designed to regulate the activities of such NGOs are functionally ineffective; and international donors face insuperable hurdles in assessing accountability.

    Immunoreactivity for a calmodulin-dependent protein kinase is selectively increased in macaque striate cortex after monocular deprivation

    Get PDF
    Immunocytochemical methods were used to localize type II Ca2+/calmodulin-dependent protein kinase in the macaque primary visual cortex. Neurons that stain for the kinase include both pyramidal and nonpyramidal cells and they appear to form a subset of cortical neurons. They are densely packed in layers II and IVB, somewhat more sparse in layers III, IVCß, and VI, and nearly absent in layer V. In normal animals the distribution of kinase-positive cells within each layer is relatively uniform. However, in animals in which one eye is removed 7-14 days before sacrifice or sutured shut for 9 or 11 weeks, the cells in layer IVCß are divided into alternating lightly and darkly stained bands. Comparison of immunocytochemically stained sections with adjacent sections stained for the mitochondrial enzyme, cytochrome oxidase, reveals that the kinase staining increases in ocular dominance columns originally driven by the removed or closed eye. These findings suggest that either the concentration of type II Ca2+/calmodulin-dependent protein kinase or its accessibility to the antibody probe increases dramatically and selectively in neurons of macaque primary visual cortex that have been deprived of their normal visual input. This may indicate that changing levels of activity in cortical neurons can alter their regulatory machinery
    corecore