Reliability analysis of consecutive k-out-of-n systems with non-identical components lifetimes

In recent years, the study of reliability properties of consecutive k-out-of-n systems has attracted a great deal of attention from both theoretical and practical perspectives. In this paper we consider linear and circular consecutive k-out-of-n systems. It is assumed that lifetimes of components of the systems are independent but their probability distributions are non-identical. We study the reliability properties of the residual lifetimes of such systems under the condition that at least (n−r+1), r≤n, components of the system are operating. We also investigate the probability that a specific number of components of the above-mentioned system operate at time t, t>0, under the condition that the system is alive at time t.     

Short Notices

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Beliefs about overconfidence

This experiment elicits beliefs about other people’s overconfidence and abilities. We find that most people believe that others are unbiased, and only few think that others are overconfident. There is a remarkable heterogeneity between these groups. Those people who think others are underconfident or unbiased are overconfident themselves. Those who think others are overconfident are underconfident themselves. Despite this heterogeneity, people overestimate on average the abilities of others as they do their own ability. One driving force behind this result is the refusal to process information about oneself: not only does this lead to overestimation of one’s own ability, but by means of social projection also to overestimation of others’ abilities.     

Mothers’ ideals and experiences of raising children in inner and outer suburban Melbourne,Australia

Parents’ perceptions of their neighbourhoods are important for child health outcomes. This study compared views among mothers in inner versus outer suburbs of Melbourne, Australia using a mixed methods approach. Mothers of preschool-aged children were recruited via playgroups, mother’s groups and preschools and interviewed face-to-face regarding their local area as a good place to raise a family, with a second open-ended interview focussing on mothers’ ideals and experiences of raising children in their current location. Findings demonstrated that mothers had different ideals for, and experiences of, raising their children in their neighbourhoods. Inner suburban mothers valued a manageable work/family balance and access to public transport over the size of their homes. However, access to childcare, secondary schooling and heavy traffic were issues, with the latter two being reasons for moving from the municipality. In contrast, outer suburban mothers preferred a larger home in neighbourhoods that they perceived as low crime, over accessibility to work. Access to a car and activities for their children were also important. Findings suggest no ‘one size fits all’ in respect to what features mothers expect from a good place to raise a family, or how they experience these features. This has implications for service delivery and social planning of suburbs.     

Pregnancy-related dropouts and gender inequality in education: A life-table approach and application to Cameroon

In this study, I used a life-table approach to estimate how much hypothetical reductions in pregnancy-related dropouts would help close the gender gap in educational attainment. Using the schooling histories of 6,686 pupils, I partitioned Cameroon's gender gap in education into "pregnancy-related" and "non-pregnancy-related" components and simulated the impact of reductions in pregnancy-related dropouts on this gap. The results suggest that such reductions would have substantial payoffs in this setting, but payoffs would be the greatest where societies also address gender inequities before puberty and outside the realm of pregnancy. Reductions in pregnancy-related dropouts complement but do not replace efforts to reduce gender discrimination in schooling. Recent data from Demographic and Health Surveys should make it possible to extend this analysis to other countries.     

The Transport System and Society’s Metabolism in the UK

This paper analyses the interrelation between the transport system and measures of resource consumption such as material and energy consumption over a 60-year period (1937–1997) in the UK. Non-motorized transport and time consumption for mobility are estimated in addition to conventional measures of transport. During the period analyzed, the UK population grew by 20% while transport of goods and persons increased more than threefold and material and energy consumption almost doubled. The transport intensity of domestic material input (DMI) doubled to 300 ton-kilometers (tkm) per ton of DMI while the transport intensity of domestic energy consumption (DEC) doubled to 20 tkm per gigajoule (GJ) of DEC. Thus, while the material and energy intensity of GDP declined significantly, a well-established trend in many advanced countries, the transport intensity of materials and energy consumption rose. These findings suggest a close link between transport, economic development, and long-term structural transformations. In the case of personal transport, a rebound effect was also observed: whereas the average speed of transport has greatly increased, the average number of hours per day devoted to personal transport has not declined.     

The impact of cash-benefit reform on parents’ labour force participation

This paper evaluates the impact of a recent Norwegian family-policy reform. The reform provides benefits of up to NOK 3,000 (approximately € 400) per month to families with one- to three-year-old children, who do not utilize state-subsidized day-care centres. We investigate the reforms effect on parents labour force participation. We find that, on average, the reform reduced womens labour force participation and increased the specialization of work between couples. We find that the effect of the reform depends on womens schooling. Specifically, the labour force participation of highly educated mothers fell by more than that of mothers with less education.I am grateful to Associate Professor Espen Bratberg and Professor Alf Erling for their valuable comments. My special thanks to Kjell Vaage, Arild Aakvik and Afsane Bjorvatn for helpful suggestions. This paper was presented in a seminar at the Department of Economics, University of Bergen, Norway. I am thankful to the participants of the seminar for their positive feedback. The paper has also benefited from the reports given by three anonymous referees. I am also thankful to Professor Heather Joshi for helpful remarks on the paper. Responsible editor: Christoph M. Schmidt.     

Have the relative employment prospects for the low-skilled deteriorated after all?

Has the relative unemployment propensity for the low-skilled increased during the 1990s? We address this question empirically, based on two notions of low skills; i) low education, and ii) low ability, conditioned on education and work experience. Ability is identified by previous earnings. Evaluated by the education-based measure, we find that unemployment propensity has not developed unfavourably for the low-skilled. Evaluated by the ability-based measure, it has. We uncover a steady deterioration of employment prospects for persons with low ability relative to others with similar formal qualifications. The adverse employment effects of being low-skilled are stronger the higher is formal education.All correspondence to Knut Røed. The paper is part of the project Sorting, exposed groups and labour market programs financed by the Research Council of Norway. We wish to thank Rolf Aaberge, Paul Gertler, Harald Goldstein, Karl Ove Moene, Jon Strand, Steinar Strøm, Asbjrn Rødseth and an anonymous referee for helpful comments. Responsible editor: John F. Ermisch.     

The fertility contribution of Mexican immigration to the United States

Crucial to the long-term contribution of immigration to a receiving country's population is the extent to which the immigrants reproduce themselves in subsequent, native-born generations. Using conventional projection methodologies, this fertility contribution may be poorly estimated primarily because of problems in projecting the number of immigrants who are at risk of childbearing. We propose an alternative method that obviates the need to project the number of immigrants by using the full sending-country birth cohort as the risk group to project their receiving-country childbearing. This "sending-country birth cohort" method is found to perform dramatically better than conventional methods when projecting to 1999 from base years both before and after the large increase in inflows of Mexican immigrants to the United States in the late 1980s. Projecting forward from 1999, we estimate a cumulative contribution of Mexican immigrant fertility from the 1980s to 2040 of 36 million births, including 25% to 50% more births after 1995 than are projected using conventional methods.