A nonlinear long memory model, with an application to US unemployment

Two important empirical features of US unemployment are that shocks to the series seem rather persistent and that it seems to rise faster during recessions than that it falls during expansions. To jointly capture these features of long memory and nonlinearity, we put forward a new time series model and evaluate its empirical performance. We find that the model describes the data rather well and that it outperforms related competitive models on various measures of fit.     

MUTUAL FUND MORTALITY, 12B‐1 FEES,AND THE NET EXPENSE RATIO

The Securities and Exchange Commission is currently reviewing Rule 12b‐1, which governs how fund advisors may pay for the distribution of fund shares. We provide evidence that even after adjusting for economies of scale, funds with 12b‐1 fees have higher expense ratios net of the 12b‐1 fees than do funds without such fees. This finding suggests that 12b‐1 fees are more than just a deadweight cost. We also demonstrate that 12b‐1 fees are highest for funds that ultimately fail, that the proportion of funds with 12b‐1 fees is increasing over time, and that the level of those fees is also increasing over time.     

The determinants of rural and urban household poverty in the North West province of South Africa

Based on standard poverty measures, the extent of poverty in the North West province is on average worse than in South Africa. For instance, the poverty gap ratio for North West is twice that of the South African average, and the FGT index is three times as high. This article therefore aims to identify the determinants of rural and urban poverty in the North West province of South Africa. Using data gathered from a survey of 593 black households across the province, probit model estimates suggest that the major significant determinants of household poverty in both rural and urban areas are education and household size. A difference between rural and urban poverty is, first, that extra female adults in a rural household raise the probability of poverty. Secondly, having a migrant (out) worker as head of the household in rural areas lowers the probability of poverty, while this does not apply to urban households. A sensitivity analysis for the robustness of the results over a range of poverty lines reveals that the impact of education is much stronger for poorer households than for more wealthy households.     

Absence management and the issues of job retention and return to work

Strategies aimed at facilitating the job retention and return to work of sick and injured workers are currently the subject of growing attention. In this article the authors examine the nature and potential significance of such strategies to absence management and utilise interview findings to shed light on current employer policies and practices relating to the management of long‐term absences. They conclude that at the national level a large proportion of working days lost through sickness absence stem from relatively long spells of absence and that the adoption of a proactive approach to supporting the return to work of ill and injured workers can have beneficial consequences. However, they further conclude that few organisations appear to have comprehensive arrangements in place to handle cases of long‐term absence. A number of areas where present employer arrangements could usefully be reviewed are therefore identified.     

Matching Supply and Demand: The Value of a Second Chance in Producing Seed Corn

This paper analyzes the supply chain for hybrid seed corn in which there are two sequential production periods with random yields before demand occurs. We show that the problem of managing the supply chain can be viewed as a multiperiod optimization model that is easily solved. By examining data that represents actual costs, prices, and yields encountered in the seed corn industry, we gain some insight into the value that the second production period provides. Using a representative sample of hybrids from a major seed corn producer, we show that margins could be enhanced considerably by using the model.     

Liquidity risk and arbitrage pricing theory

Classical theories of financial markets assume an infinitely liquid market and that all traders act as price takers. This theory is a good approximation for highly liquid stocks, although even there it does not apply well for large traders or for modelling transaction costs. We extend the classical approach by formulating a new model that takes into account illiquidities. Our approach hypothesizes a stochastic supply curve for a securitys price as a function of trade size. This leads to a new definition of a self-financing trading strategy, additional restrictions on hedging strategies, and some interesting mathematical issues.Received: 1 November 2003, Mathematics Subject Classification: 60G44, 60H05, 90A09JEL Classification: G11, G12, G13Umut Çetin: This work was performed while Dr. Çetin was at the Center for Applied Mathematics, Cornell UniversityPhilip Protter: Supported in part by NSF grant DMS-0202958 and NSA grant MDA-904-03-1-0092 The authors wish to thank M. Warachka and Kiseop Lee for helpful comments, as well as the anonymous referee and Associate Editor for numerous helpful suggestions, which have made this a much improved paper.