A STUDY OF AUTOMOBILE INVENTORY INVESTMENT

The volatile fluctuations in automobile inventory levels are explained well by the stock-adjustment model estimated in this paper on monthly time-series data. In contrast to the findings of most previous inventory studies, fluctuations in financial inventory carrying costs (as measured by a service cost of capital) are found to influence the target auto stocks in both a statistically significant and economically important manner. Also, the speed-of-adjustment of automobile inventories to their target level is estimated to be relatively fast, about thirty percent per month.     

RACE AND HOME OWNERSHIP: IS DISCRIMINATION DISAPPEARING?

Racial differentials in home ownership rates are examined using data on households in the twenty-four largest metropolitan areas. considerable recent reduction in racial discrimination is indicatd, in contrast to the findings of a previous analysis of the St. Louis housing market. The results are maintained under a number of modifications of the model and estimation technique.     

Setups and effective capacity: the impact of lot sizing techniques in an MRP environment

This study investigates how lot sizing techniques influence the profit performance, inventory level, and order lardiness of an assembly job shop controlled by MRP. Four single-level lot sizing techniques are compared by simulation analysis under two levels of master schedule instability and two levels of end item demand. A second analysis investigates the influence of a multilevel lot sizing technique, the generalized constrained-K (GCK) cost modification, on the four single-level techniques at low demand and low nervousness. The analyses reveal a previously unreported phenomenon. Given the same inventory costs, the single-level lot sizing techniques generate substantially different average batch sizes. The lot sizing techniques maintain the following order of increasing average batch size (and decreasing total setup time):

economic order quantity (EOQ)

period order quantity (POQ)

least total cost (LTC)

Silver-Meal heuristic (SML)

The causes for different average batch sizes among the lot sizing techniques are analysed and explained. Demand lumpiness, inherent in multilevel manufacturing systems controlled by MRP, is found to be a major factor. The number of setups each lot sizing technique generates is the primary determinant of profit performance, inventory level, and order tardiness. EOQ, a fixed order quantity technique, is less sensitive to nervousness than the discrete lot sizing techniques. EOQ_, however, generates the smallest average batch size, and, therefore, the most setups. Since setups consume capacity, EOQ, is more sensitive to higher demand. SML generates the largest average batch sizes, and is, therefore, less sensitive to increased demand. At low demand, the other lot sizing techniques perform better on all criteria. They generate smaller batches and, therefore, shorter actual lead times. The GCK cost modification increases the average batch size generated by each lot sizing technique. GCK improves the profit and customer service level of EOQ the lot sizing technique with the smallest batches. GCK causes the other lot sizing techniques to generate excessively large batches and, therefore, excessively long actual lead times.     

Evaluation of a class-based storage scheduling technique applied to dual-shuttle automated storage and retrieval systems

Research to improve the performance of automated storage and retrieval systems has concentrated on developing more effective system designs or scheduling control programs to reduce the time a shuttle spends travelling in a rack. Sarker et al. (1991) showed that a dual-shuttle AS/RS operating under a nearest-neighbour scheduling model would significantly improve system throughput performance over a single-load shuttle system. The study was limited in that it only considered dual-shuttle improvements under the nearest-neighbour model. This research exploits the benefits of a dual-shuttle system by integrating the technology with a more effective scheduling technique, the class-based storage model, for reducing the shuttle travel time. The dual-shuttle, class-based storage model produced a significant reduction in shuttle travel time and thus higher throughput results over the dual-shuttle, nearest-neighbour model. This study further supports the premise that a dual-capacity shuttle is an effective way of improving the productivity of an automated storage and retrieval system.     

PAID- VERSUS DONATED-MEDIA STRATEGIES FOR PUBLIC SERVICE ANNOUNCEMENT CAMPAIGNS

Public service announcement (PSA) campaigns have traditionallyrelied on donated rather than paid advertising media. Recently,however, both government agencies and charitable or ganizationshave questioned whether donated-media strategies should be abandonedfor paid-media PSA campaigns. The present research examinesthis issue in a three-market field experiment comparing theeffectiveness of "paid versus donated" PSA cam paigns in decreasingyouthful male drinking and driving. Depen dent variables include(1) self-reports of behaviors from sample surveys and (2) officialcounts of incapacitating and fatal highway accidents. Resultsshow that both campaigns were equally effec tive and both werecost efficient. Thus, in light of these results, it is recommendedthat social marketers not abandon donated-media PSA campaignsfor paid-media PSA campaigns.     

MEASURING CRACK COCAINE AND ITS IMPACT

Numerous social indicators turned negative for Blacks in the 1980s and rebounded a decade later. We explore whether crack cocaine explains these patterns. Absent a direct measure, we construct a crack prevalence index using multiple proxies. Our index reproduces spatial and temporal patterns described in ethnographic accounts of the crack epidemic. It explains much of the 1980s rise in Black youth homicide and more moderate increases in adverse birth outcomes. Although our index remains high through the 1990s, crack's deleterious social impact fades. Changes over time in behavior, crack markets, and the user population may have mitigated crack's damaging impacts. (JEL K42, J15, I30)     

Marital Shopping and Epidemic AIDS

HIV risks decline sharply at age 30 for women in South Africa, long before coital frequencies or pregnancies decrease. I evaluate several prominent behavioral models of HIV, and find that these do not suggest sharply decreasing risks with age. I formulate a model of spousal search and find that “marital shopping” can generate epidemic HIV prevalence despite low transmission rates because search behavior interacts with dynamics of HIV infectiousness. The implied age-infection profile closely mimics that in South Africa, and the suggested behavior matches that reported by South Africans. Condom use in new relationships and transmission rate reductions are both found to be effective policies and, when used together, eliminate the potential of spousal search to spread HIV. In contrast, antiretroviral treatment is found to have only a minimal effect on the epidemic.     

ECONOMIC REGULATION IN MERCANTILE EENGLAND: HECKSCHER REVISITED

The gradual evolution to free enterprise in England, which became quite pronounced about the time of Adam Smith, is explained in this paper in terms of institutional changes in the rent-seeking society of mercantile England. In this explanation the role of ideas and influential writers is seen as subsidiary to the role of real economic and institutional forces in producing historical outcomes. Moreover, a major feature of our rent-seeking interpretation is that the poor design and competition for control of the mercantile regulatory process unintentionally helped bring about the institutional changes which made rent seeking and economic regulation by the central government less feasible.
"a part of that force which always intends evil 4und always creates good"— Goethe, Faust.