Bounds for expectations of concomitants

We present sharp bounds on expected values of concomitants based on a sample of identically distributed random pairs. The dependence between pair components is described by regression functions or modelled by copulas, or generated by sampling without replacement from finite populations.     

Floral biodiversity of allotment gardens and its contribution to urban green infrastructure

Allotment gardens are a key feature of the urban landscape, providing numerous benefits beyond those of food production. These include ecosystem services such as local climate modification, pollination, and providing a pleasant location for socialising. The biodiversity of flora underpins many of these ecosystem services. The aims of this study are to assess the spontaneous vascular flora of urban allotment gardens and derive estimates of the species richness and diversity. In doing so, the specific position of allotment gardens within urban green infrastructure will be revealed and the role of allotment users in shaping local biodiversity determined. 358 species of spontaneous flora were recorded in 11 representative allotment garden estates (total area 150 ha) in Poznań, Poland. Fourteen biodiversity features were taken into account. The investigated areas exhibited high plant species richness, high diversity, low synanthropisation level, and contained valuable geobotanical elements, including plants of key importance for the European Community. For these reasons, allotment gardens should be considered as biodiversity hotspots for native species within urban green infrastructure. Based on an analysis of the spatial and functional organization of 110 individual plots, four types of usage, and corresponding plant diversity have been distinguished. The composition of the flora depends mostly on spatial and functional organization of allotment gardens and, to a much lesser extent, on the habitat conditions, which on individual plots varied very little. The high species richness and diversity in allotment gardens has important consequences for urban planning.     

Patterns,Determinants, and Implications of Intermarriage Among Arab Americans

This study examines Arab American intermarriage using 1990 U.S. Census data. The results indicate high rates of intermarriage consistent with an assimilation perspective. Over 80% of U.S.‐born Arabs had non‐Arab spouses, implying a diminishing ethnic identification. Logistic regressions show that for both sexes, those with part Arab ancestry, the U.S. born, those with strong English‐language ability, and the highly educated were significantly more likely to out‐marry, as were Arabs of Lebanese ancestry. The cultural and structural assimilation of Arab Americans is facilitating intermarriage, with indicators of acculturation being the strongest predictors, especially for women. The article further discusses ethnic options for children of intermarried couples.     

Uncertainty about Uncertainty and Delay in Bargaining

We study a one‐sided offers bargaining game in which the buyer has private information about the value of the object and the seller has private information about his beliefs about the buyer's valuation. We show that this uncertainty about uncertainties dramatically changes the set of outcomes. In particular, second order beliefs can lead to a delay in reaching agreement even when the seller makes frequent offers. We show that not all types of second order beliefs lead to a delay. When the buyer assigns positive probability to the seller knowing the buyer's value, then delay not only can occur, but it must occur for a class of equilibria. However, in all other cases delay will never occur.     

友谊奖外国专家辽宁行——我的亲身感受

就在我刚结束在波兰的假期之时．我被告知国家外国专家局邀请我和夫人参加辽宁之行,这真是一个巨大的惊喜。我感到非常荣幸和高兴,因为在我5年的中国生活中,还从未到过辽宁。     

The Role of Information in Repeated Games With Frequent Actions

We show that in repeated interactions the avenues for effective provision of incentives depend crucially on the type of information players observe. We establish this conclusion for general repeated two‐player games in which information arrives via a continuous‐time stationary process that has a continuous multidimensional Brownian component and a Poisson component, and in which the players act frequently. The Poisson jumps can be used to effectively provide incentives both with transfers and value burning, while continuous Brownian information can be used to provide incentives only with transfers.     

Ecological lands for conservation of vascular plant diversity in the urban environment

Conservation of biodiversity in urban areas has become crucial to urban green area management. There are several legislative solutions for preservation of species and habitats in cities. One of them is ‘ecological lands’ – a low-restrictive form of protected areas in Poland. We aimed to assess their efficiency in vascular flora biodiversity conservation in the urban environment in Poznań (W Poland; 550,000 inhabitants). We hypothesized that ecological lands which cover <2% of the city area comprise over 50% of taxonomic diversity and over 90% of functional trait-level range of the vascular flora. Analysis of five ecological lands, which covered 1.8% of the whole city area confirmed our hypothesis. In ecological lands studied, we found 564 species of vascular plants, which is 52.9% of the whole city flora. These species belonged to 23 of 29 phytosociological classes represented in the whole city (73.9%). Functional trait distributions in ecological lands studied comprised from 95.8 to 100% of trait distributions in the flora of the whole city. Ecological lands seem to be a good way for conservation of biodiversity in urban areas. The legislative simplicity and low restrictiveness for both land management and recreational utility make ecological lands a much easier form of nature conservation which may be adapted to other cities for more efficient biodiversity management.     

Time Horizon and Cooperation in Continuous Time

We study social dilemmas in (quasi‐) continuous‐time experiments, comparing games with different durations and termination rules. We discover a stark qualitative contrast in behavior in continuous time as compared to previously studied behavior in discrete‐time games: cooperation is easier to achieve and sustain with deterministic horizons than with stochastic ones, and end‐game effects emerge, but subjects postpone them with experience. Analysis of individual strategies provides a basis for a simple reinforcement learning model that proves to be consistent with this evidence. An additional treatment lends further support to this explanation.