Agricultural Extension and Imperfect Supervision in Contract Farming: Evidence from Madagascar

This article tests whether agricultural extension and imperfect supervision -- conflated here into the number of visits by a technical assistant -- increase productivity in a sample of contract farming arrangements between a processing �rm and small agricultural producers in Madagascar. Production functions are estimated which treat the number of visits by a technical assistant as an input and which exploit the variation in the number of visits between the contracted crops grown on a given plot by a speci�c grower, thereby accounting for district-, grower-, and plot-level unobserved heterogeneity. Results indicate that the elasticity of yield with respect to the number of visits lies between 1.3 and 1.7.Supervision, Extension, Contract Farming, Grower-Processor Contracts

Professor McGrath Offers a Scholarly Take \u3cem\u3eOn Religion and Doctor Who\u3c/em\u3e

Take TV viewers on trips through time and space for 50 years and you’re going to pick up some admirers—including some scholarly ones. That’s what’s happened with Doctor Who, the British series that is celebrating 50 years this month.Two of the show’s fans—Butler University Professor of Religion James McGrath and Andrew Crome, a lecturer in the history of modern Christianity at the University of Manchester (England)—have compiled a new book, Time and Relative Dimensions in Faith: Religion and Doctor Who, in which 19 scholars who also are Doctor Who fans weigh in on how the longest-running science fiction series in television history deals with religious topics

The (Im)Possibility of Reverse Share Tenancy

Under the assumption that the landlord is risk-neutral and the tenant is risk-averse, sharecropping is second-best in that it trades off risk sharing and incentives. Many, however, have reported instances of reverse share tenancy, or sharecropping in which the landlord is considerably poorer than the tenant. This note shows that reverse share tenancy is impossible under the canonical Stiglitzian model of sharecropping but becomes possible if and only if (i) both the landlord and the tenant can be assumed risk-averse; or (ii) there exist significant transactions costs making sharecropping more desirable than either a wage or fixed rent contract.Sharecropping; Reverse Share Tenancy; Transactions Cost

The Supersymmetric Leptophilic Higgs Model

In the leptophilic model, one Higgs doublet couples to quarks and another couples to leptons. We study the supersymmetric version of this model, concentrating on the tightly constrained Higgs sector, which has four doublets. Constraints from perturbativity, unitarity, and LEP bounds are considered. It is found that the lightest Higgs, h, can have a mass well below 114 GeV, and for masses below 100 GeV will have a substantially enhanced branching ratio into tau pairs. For this region of parameter space, traditional production mechanisms (Higgs-strahlung, W fusion and gluon fusion) are suppressed, but it may be produced in the decay of heavier particles. The second lightest Higgs has a mass of approximately 110 GeV for virtually all of parameter space, with Standard Model couplings, and thus an increase of a few GeV in the current lower bound on the Standard Model Higgs mass would rule out the model. The two heavier Higgs are both gauge-phobic, one decays almost entirely into b pairs and can be produced via gluon fusion while the other decays almost entirely into tau pairs but can't be easily produced.Comment: 21 pages, 6 figure

Refined bound for sum-free sets in groups of prime order

Improving upon earlier results of Freiman and the present authors, we show that if $p$ is a sufficiently large prime and $A$ is a sum-free subset of the group of order $p$, such that $n:=|A|>0.318p$, then $A$ is contained in a dilation of the interval $[n,p-n]\pmod p$

Generalized Gamma Convolutions, Dirichlet means, Thorin measures, with explicit examples

In Section 1, we present a number of classical results concerning the Generalized Gamma Convolution (:GGC) variables, their Wiener-Gamma representations, and relation with the Dirichlet processes.To a GGC variable, one may associate a unique Thorin measure. Let $G$ a positive r.v. and $\Gamma_t(G)$ (resp. $\Gamma_t(1/G))$ the Generalized Gamma Convolution with Thorin measure $t$-times the law of $G$ (resp. the law of $1/G$). In Section 2, we compare the laws of $\Gamma_t(G)$ and $\Gamma_t(1/G)$.In Section 3, we present some old and some new examples of GGC variables, among which the lengths of excursions of Bessel processes straddling an independent exponential time.Comment: Published in at http://dx.doi.org/10.1214/07-PS118 the Probability Surveys (http://www.i-journals.org/ps/) by the Institute of Mathematical Statistics (http://www.imstat.org