In search of an evolutionary edge: trading with a few, more, or many

Consider a population of farmers who live around a lake. Each farmer engages in trade with his m adjacent neighbors, where m is termed the “span of interaction.” Trade is governed by a prisoner’s dilemma “rule of engagement.” A farmer’s payoff is the sum of the payoffs from the m prisoner’s dilemma games played with his ^m/₂^m/_2 neighbors to the left, and with his ^m/₂^m/_2 neighbors to the right. When a farmer dies, his son takes over. The son who adheres to his father’s span of interaction decides whether to cooperate or defect by considering the actions taken and the payoffs received by the most prosperous member of the group comprising his father and his father’s m trading partners. Under a conventional structure of payoffs, it is shown that a large span of interaction is detrimental to the long-run coexistence of cooperation and defection, and conditions are provided under which the social outcome associated with the expansion of trade when individuals trade with a few is better than that when they trade with many. Under the stipulated conditions it is shown, by means of a static comparative analysis of the steady state configurations of the farmer population, that an expansion of the market can be beneficial in one context, detrimental in another.     

Adoption of organic farming: Are there differences between early and late adoption?

Based on the fact that not all farmers adopt a technology at the same time, it is argued in this paper that the distinction between groups is important because early, medium and late adopters respond differently to economic and non-economic factors when they consider whether to take up organic farming or not. The individual effects on adoption between the groups are identified by the use of multinomial logit analysis. The results provide evidence that there are significant differences in the characteristics between the adopter groups. The findings also reveal that the factors that affect adoption play a different role for early, medium and late adopters, particularly with regard to farming intensity, age, information gathering as well as attitudes of the farmer. More specifically, early adopters were the youngest to adopt organic farming and their decisions were found to be less profit related compared to other groups. Late adoption is constrained by risk considerations, while environmental attitudes and social learning were identified to be important determinants for all adopter groups. Overall, the findings strongly suggest, that for policy measures to be effective, the current state of diffusion has to be taken into account.     

Comparaison de la rentabilité des systèmes conventionnels et biologiques en production laitière au Québec

De la banque de données AGRITEL, 336 fermes conventionnelles et 16 fermes biologiques, spécialisées en production laitière, sont sélectionnées. Sept groupes (dont un est biologique) sont alors formés correspondant à des concepts de production différents. Les groupes defermes conventionnelles correspondent à des niveaux d'intrants particulièment élevés (haut niveau d'intrants) ou faibles (bas niveau d'intrants), ainsi qu'à des niveaux de production élevés @roduction intensive) oufaibles (production extensive), pour le troupeau ou pour l'ensemble de l'entreprise.
Les fermes biologiques parviennent à des résultats technico-économiques et financiers au moins aussi bons que les fermes avec des rendements élevés (intensifs). En revanche, même si les concepts de production sont proches, les différences de rendement et de rentabilité sont assez nettes (souvent signcatives) entre le groupe biologique et les groupes extensifs ou à bas niveau d'intrants. Les entreprises biologiques sont plus équilibrtés et la prédominance de la production laitière est moindre. Les coûts de main-d'œuvre sont toutefois plus élevés que la plupart des groupes d'entreprises conventionnelles.
Cette étuaè nous laisse croire qu'il est possible d'amtéliorer la rentabilité des fermes extensives et à bas niveau d'intrants, dont les concepts de production se rapprochent de ceux de l'agriculture biologique.     

Testing for Discrimination against Lesbians of Different Marital Status: A Field Experiment

In this paper, I conduct a correspondence testing experiment to examine sexual orientation discrimination against lesbians in Germany. I sent applications from four fictional female characters in response to job advertisements in Munich and Berlin: a heterosexual single, a married heterosexual, a single lesbian, and a lesbian who is in a “same‐sex registered partnership.” While single lesbians and lesbians in a registered partnership are equally discriminated in comparison to the heterosexual women in the city of Munich, I found no discrimination based on sexual orientation in Berlin. Furthermore, for a subset of the data we can compare the effects of a randomized versus a paired testing approach, which suggests that under certain conditions, due to increased conspicuity, the paired testing approach may lead to biased results.     

On the evolutionary edge of migration as an assortative mating device

In a haystack-type representation of a heterogeneous population that is evolving according to a payoff structure of a prisoner’s dilemma game, migration is modeled as a process of ‘swapping’ individuals between heterogeneous groups of constant size after a random allocation fills the haystacks, but prior to mating. Migration is characterized by two parameters: an exogenous participation-in-migration cost (of search, coordination, movement, and arrangement-making) which measures the migration effort, and an exogenous technology—of coordinating and facilitating movement between populated haystacks and the colonization of currently unpopulated haystacks—which measures the migration intensity. Starting from an initially heterogeneous population that consists of both cooperators and defectors, a scenario is postulated under which ‘programmed’ migration can act as a mechanism that brings about a long-run survival of cooperation.