This article evaluates the effects of a November 2004 phytosanitary rule that removed seasonal and geographic restrictions on the importation of fresh Hass avocados from approved orchards in Mexico to the United States. With the remaining systems approach compliance measures in place, pest risks do not substantially increase and U.S. net welfare rises by $77 million. Removal of remaining compliance measures may lead to lower net welfare gains depending on which measures are eliminated and the estimated probabilities of pest infestations. Copyright 2008, Oxford University Press.

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Pointed pseudo-triangulations are planar minimally rigid graphs embedded in the plane with pointed vertices (incident to an angle larger than π). In this paper we prove that the opposite statement is also true, namely that planar minimally rigid graphs always admit pointed embeddings, even under certain natural topological and combinatorial constraints. The proofs yield efficient embedding algorithms. They also provide-to the best of our knowledge-the first algorithmically effective result on graph embeddings with oriented matroid constraints other than convexity of faces.

This paper presents support for long-run monetary neutrality based on evidence that individual time series for money, manufacturing prices, and agricultural prices are nonstationary but cointegrated, with a stationary proportional long-run relationship among their levels. Dynamic simulations from a vector error-correction model with this restriction imposed show that monetary shocks shift relative prices in favor of agriculture in the short run and permanently raise nominal prices. Manufacturing price shocks have similar long-run effects but initially place agriculture in a cost-price squeeze, while agricultural price shocks are transitory and have little impact on the other series.

We prove that for every centrally symmetric convex polygon Q, there exists a constant α such that any αk-fold covering of the plane by translates of Q can be decomposed into k coverings. This improves on a quadratic upper bound proved by Pach and Tóth (SoCG'07). The question is motivated by a sensor network problem, in which a region has to be monitored by sensors with limited battery lifetime.

Growth of French agriculture is addressed with production disaggregated among cereals, noncereal crops, milk, and animal products. Short-run and long-run supply functions are derived from a restricted profit function model in which capital and family labor are assumed quasi-fixed and measures of French public agricultural research expenditures and international technology availability are included. Production is found to be price responsive, but the estimated supply functions are inelastic even when the quasi-fixed factors adjust optimally. Technical change as a source of output growth is also supported. Domestic research is estimated to be the primary cause of increased cereals output over the 1960-84 period, while international technology transfers and domestic research seem to be important for milk production.

This paper characterizes environmental quality and industry protection in a large-country Gross-Helpmann model when production or consumption externalities exist and governments decide noncooperatively on domestic and trade policies. Governments choose policies efficiently from among those available, but competitive lobbies may prefer less efficient regimes. Under restricted policy availability, political-support effects can offset terms-of-trade effects on equilibration outcomes and inefficient trade policies can lead to higher environmental quality than efficient domestic policies. If governments cooperate, they can satisfy particular organized industries at lower costs to other lobbies and total welfare. This may result in lower environmental quality than noncooperation