Soil Traversing Arthropod Populations as Sampled by Pitfall Traps in Sunflower and Three Adjacent Habitats in Northeast Arkansas

Soil traversing arthropod populations were sampled by pitfall traps in sunflower (Helianthus spp.) and three adjacent habitats during the months of July, August and September of 1980 and May, June, July and August of 1981. In1980, four varieties of sunflower (Ellar, Hybrid 670, 891 and S-345) were planted. A single variety of sunflower (Ellar) was planted in1981. The three adjacent habitats in both 1980 and 1981 were a pine stand, grass border and fence row. Of 1,748 specimens collected in 1980, 17 orders and 48 families were represented. Four orders comprised 78% of the total catch: Hymenoptera (45%), Acari (17%), Collembola(11%) and Coleoptera (5%). In 1981, 20 orders and 64 families were represented in a total of 26,693 trapped specimens. Four orders composed 88% of the total catch: Collembola (57%), Acari (14%), Hymenoptera (11%) and Homoptera (6%). Family composition and seasonal occurrence are discussed and compared for habitats sampled. Weather data are presented and discussed in relation to arthropod activit

Pentatomidae of Arkansas

A total of 30 genera and 53 species and subspecies of Pentatomidae are reported as occurring or possibly occurring in Arkansas. Fifty species and subspecies contained in 29 genera were collected or recorded from previously collected material. Based on distributional records in the literature, three additional species and one genus are listed as probably occurring in Arkansas. County and seasonal records are reported for each taxon

Unit Vs. Ad Valorem Taxes in Multi-Product Cournot Oligopoly

The welfare dominance of ad valorem taxes over unit taxes in a single-market Cournot oligopoly is well-known. This article extends the analysis to multi-market oligopoly. Provided all ad valorem taxes are positive, unit costs are constant, firms are active in all considered markets, and a representative consumer has convex preferences, it is shown that ad valorem taxes dominate in multi-product equilibrium. We discuss the role of unit cost covariances across multi-product firms in determining the extent of cost efficiencies arising under ad valorem taxation. The issue of merger under oligopoly is also considered. Conditions are identified under which a merger increases the sum of consumer and producer surpluses while also increasing the revenue yield from a set of unit taxes. If not all firms are active in all considered markets, then it is also shown that additional conditions are required to ensure the dominance of ad valorem taxes. In multi-input Cournot oligopsony, however, unit taxation welfare dominates. This is because ad valorem taxes on inputs reduce demand elasticities, amplifying market power distortions.ad valorem tax; imperfect competition; oligopoly merger; quantity-setting game; specific tax; tax efficiency; tax revenue

Cost Arrangement and Welfare in a Multi-Product Cournot Oligopoly

Welfare in a two-product Cournot oligopoly is shown to increase (decrease) with an increase in correlation between unit costs when the outputs complement (substitute) in demand. A more qualified correlation structure is required for the result to apply in a three-product Cournot oligopoly when products complement in demand.complementarity; arrangement increasing; invariance

When Different Market Concentration Indices Agree

Market concentration ratios are popular statistics for characterizing the extent of market dominance in an imperfectly competitive market, but these ratios may not agree when comparing two markets. Neither do they necessarily agree with the Herfindahl-Hirschman or entropy indices. This letter compares two Cournot oligopoly markets in which firms have constant unit costs. It is shown that the majorization pre-ordering on normalized marketing margin vectors is both necessary and sufficient for all aforementioned indices to agree on which is the more concentrated market.

Buying Ecological Services: Fragmented Reserves, Core and Periphery National Park Structure, and the Agricultural Extensification Debate

�Growing demand for cropland products has placed intense pressure on the abilityof land resources to support nature, straining public budgets to purchase environmental goods.Fixing overall agricultural output, two environmental policy options are whether to a) promotemore agricultural extensification and nature friendly farming practices or b) produce intensivelyon some land and leave the rest wild. Microeconomic models of the topic have not accounted forwidely recognized spatial externalities regarding fragmented reserves. This article does so, usingWirtinger’s inequality to also identify a third policy possibility. This is that ecological servicescan follow a smoothly varying spatial path chararacterized by harmonic functions. We use theresults to rationalize the core and periphery National Park structure put in place around theworld, i.e., versions of our third policy possibility have been implemented.Environmental policy; Land use; National Park management; Spatial externalities; Wirtinger’s inequality

Trade Policy Under Asymmetric Information

We consider optimal trade policy for a large country with private information. We show that the optimal tariff leads to a signaling equilibrium with higher tariffs and lower welfare than under complete information, whereas the optimal import quota replicates the complete information equilibrium and thus is superior to the tariff. We also show that, with the tariff, the country may be better off being uninformed. Finally, we show that if the importing nation cannot commit to its tariff, the use of futures contracts together with the dynamically consistent tariff leads to the same equilibrium as under complete information with commitment.

Algebraic Theory of Multi-Product Decisions, An

The typical firm produces for sale a plural number of distinct product lines. This paper characterizes the composition of a firm?s optimal production vector as a function of cost and revenue function attributes. The approach taken applies mathematical group theory and revealed preference arguments to exploit controlled asymmetries in the production environment. Assuming some symmetry on the cost function, our central result shows that all optimal production vectors must satisfy a dominance relation on permutations of the firm?s revenue function. When the revenue function is linear in outputs, then the set of admissible output vectors has linear bounds up to transformations. If these transformations are also linear, then convex analysis can be applied to characterize the set of admissible solutions. When the group of symmetries decomposes into a direct product group with index K in N, then the characterization problem separates into K problems of smaller dimension. The central result may be strengthened ; when the cost function is assumed to be quasiconvex.

Taste Asymmetries and Trade Patterns

We study trade patterns in a pure exchange economy where preferences are symmetric up to taste intensity parameters. In a 2-person, 2-good endowment economy, then all endowments in a particular Edgeworth box rectangle require trading out of that rectangle. Under strictly quasi-concave preferences, trade will occur away from a larger area of initial endowments. The identified area is larger still when preferences are homothetic and identical up to taste intensity parameters. Implications for the factor price equalization theorem are explored.