Modelling heterogeneous space–time occurrences of earthquakes and its residual analysis

Summary. Earthquake intensities are modelled as a function of previous activity whose specific form is based on established empirical laws in seismology, but whose parameter values can vary from place to place. This model is used for characterizing regional features of seismic activities in and around Japan, and also for exploring regions where the actual seismicity rate systematically deviates from that of the modelled rate.     

Social Change and Social Policy in Japan

This paper aims to present and discuss social change and social policy in Japan after the mid-20th century from a sociological viewpoint. Japanese social change and social policy from the mid-20th century onward can be categorized into three models in chronological order: escape from mass poverty by means of industrialization, improvement of the social security system to establish a welfare state, and parallel progress of aspiration for a welfare society and workfare. Defined concretely, these are (1) the period that established and improved social security, which started immediately after the end of World War II and ended in 1973, when Japan began to suffer from low growth after enjoying high growth; (2) the period in which finance for social security was adjusted, halfway through which the country experienced a bubble economy; and (3) the period after the 1990s, in which the structural reform of social security went hand-in-hand with labor policy and the advent of globalization. In each of the three periods, the direction of social policy was affected by factors that caused changes in such areas as industrial structure (the decline of agriculture), demographic structure (an aging society), and family structure and work pattern (the growing trend of nuclear families, single-person households, and irregular employment). In Japan, life security now attracts increasing attention, and employment security rather than social security has been the central issue. As it is greatly affected by globalization, employment security grows less conspicuous and makes the vulnerability of social security grow more conspicuous. Social policy has the potential to become an area with which to struggle for national integration and fissures between social groups.     

Contest and scramble competitions in two bruchid species,Callosobruchus analis andC. Phaseoli (Coleoptera: Bruchidae)

Summary We performed multiple-generation competition experiments betweenCallosobruchus analis andC. phaseoli with different bean sizes. In each system, we supplied 5 g of mung beans (Vigna radiata) every 10 days. We examined three types of bean conditions: 5 g of large beans, 5 g of small beans, and a mixture of 2.5 g of large and small beans. In small bean condition,C. analis dominatedC. phaseoli in all three replicates andC. phaseoli was extinct by the 260th day. On the contrary,C. phaseoli overcameC. analis within 250 days in large beans in all three replicates. In mixed beans condition the two bruchid species coexisted more than 500 days in two out of the three replicates. Even in the exceptional case, both species coexisted for 460 days. These results were examined in the light of the predictions from short-term larval competition experiments and a game theoretical model by Smith and Lessells (1985). The density and frequency dependent results during larval competition inside a bean was concluded to be a main factor to produce the above long-term competition results.     

Do Irrelevant Commodities Matter?

We study how to evaluate allocations independently of individual preferences over unavailable commodities. We prove impossibility results that suggest that such evaluations encounter serious difficulties. This is related to the well known problem of performing international comparisons of standard of living across countries with different consumption goods. We show how possibility results can be retrieved with restrictions on the domain of preferences, on the application of the independence axiom, or on the set of allocations to be ranked. Such restrictions appear more plausible when the objects of evaluation are allocations of composite commodities, characteristics, or human functionings rather than ordinary commodities.     

Niche modification and stability of competitive systems. III. Simulation model analysis

Summary Simulation model for niche shift in ecological time scale was constructed on the basis of the optimal foraging theory. In accordance with the previous experimental study (Shimada andFujii, 1985), the model competitive system consisted of 2 parasitoid wasp species utilizing 4 host stages. Wasps were assumed to choose host stages in the manner that they realized the maximal gain/cost values, where gain was represented by body weight of a wasp progeny emerging from each host stage and cost was expressed by time required to search for and detect an unparasitized host. The number of parasitized hosts in each host stage was calculated numerically by usingArditt's (1983) model for avoidance of superparasitism. The model simulated well the experimental results ofShimada andFujii (1985) andShimada (1985). Sensitivity analysis of the model showed that the experimentally derived criterion for competitive coexistence (different second-best host stages between competing species even with the common best) was not necessarily the indispensable condition for niche shift and separation, but that if the criterion was not satisfied, stable competitive coexistence occurred only in the narrow range of the parametric values. Further, niche shift in ecological time scale made the competitive coexistence more stable than fixed niche on which the current niche theory stands.     

Egalitarian-equivalence and the Pareto principle for social preferences

The Pareto principle is often in conflict with the equity criteria in construction of social preferences: there exist two allocations x and y such that x Pareto dominates y, but y is an equitable allocation whereas x is not. The efficiency-first principle requires to rank an allocation x higher than y if (i) x Pareto dominates y or (ii) x and y are Pareto-noncomparable and x is equitable whereas y is not. The equity-first principle reverses the order of application of the two criteria. Adopting egalitarian-equivalence as the notion of equity, we examine rationality of the social preference functions based on the efficiency-first or the equity-first principle. The degrees of rationality vary widely depending on which principle is adopted, and depending on the range of egalitarian-reference bundles. We show several impossibility and possibility results as well as a characterization of the social preference function introduced by Pazner and Schmeidler (1978). We also identify the sets of maximal elements of the social preference relations in the set of feasible allocations. The results are contrasted with those in the case where no-envy is the notion of equity.This paper is a much extended version of a part of Tadenuma (1998). The author is grateful to Marc Fleurbaey, Serge-Chiristophe Kolm, Kotaro Suzumura, and William Thomson for helpful comments on the earlier version of the paper. ‘‘Financial support from the Ministry of Education, Culture, Sports, Science and Technology of Japan for the 21st Century Center of Excellence Project on the Normative Evaluation and Social Choice of Contemporary Economic Systems is gratefully acknowledged’’.     

The challenge of keeping Japanese older people economically active

Japanese society faces serious problems due to population ageing. Both the number and percentage of people aged 65 years old and over are increasing. The ratio of those aged 65+ was 17.3 per cent in 2000, but the estimate of the National Institute of Population and Social Security Research is that the ratio will become 28.7 per cent in 2025 and will reach 40 per cent in 2050. This article consists of four sections. In the first the characteristics of issues associated with population ageing in Japan are discussed. The actual situations of employment and lives of older workers are introduced. The second section analyses government policies to address the ageing of the population. The Japanese government is trying to address the issue through encouraging older people to work longer. The promotion of efforts to extend longer working lives is discussed. In the third section a rehiring system and two cases of Japanese firms are described. Those enterprises are effectively employing older workers. Their experiences would be interesting for those planning to hire older workers. The last section discusses how to resolve challenges associated with population ageing. It is shown that continuous training is one of the most important ways of keeping older people productive.     

An island biogeographical approach to the analysis of butterfly community patterns in newly designed parks

We analyzed the butterfly communities in the newly designed city parks (area C), “newly opened habitat islands”, of Tsukuba City, central Japan. The area constituted a natural ecological experiment on the mainland for clarifying the pattern and process of faunal immigration. We compared butterfly communities in area C with those in two other areas in the light of the theory of island biogeography and the concept of generalist/specialist. Our results showed the following: (1) Fewer species were found in area C than in other areas, due largely to the absence of many specialist types, restricted and habitat specialists, and/or low density species in the area. Generalist types, widespread and habitat generalists, and/or high density species predominated in area C. (2) The difference in the species numbers among the three sections within area C could be explained by the habitat structure in and around the respective sections. (3) The densities of many species were low in area C, probably due to its man-modified habitat structure. In particular, several species occurred at extremely low densities in area C, but at high densities in other areas. (4) The internal structure of the habitat island butterfly community in area C was almost perfectly consistent with that of “quasi-equilibrium” communities that appear during the colonization of an island. Our results demonstrate that the synergetic application of the generalist/specialist concept and the island biogeography theory is effective for the understanding of the patterns and structures of habitat island communities.