KwaZulu-Natal Income Dynamics Study (KIDS) 1993–98: A longitudinal household database for South African policy analysis

An important adjunct of apartheid has been the absence of credible and comprehensive data on which policies, such as poverty reduction strategies, can be grounded. The 1993 Project for Statistics on Living Standards and Development (PSLSD) provided the first comprehensive household database for South Africa. Despite its usefulness, however, the one round PSLSD cannot provide answers to many questions important to policy researchers and practitioners, particularly questions about dynamic processes. The primary objective in this article is to introduce a new longitudinal household database, based on the PSLSD, which begins to fill this gap. Households surveyed by the PSLSD in KwaZulu-Natal province were re-surveyed in 1998 by the KwaZulu-Natal Income Dynamics Survey (KIDS). As a research endeavour, the KIDS project addresses one of the most vexing and important problems confronting contemporary South Africa: understanding the forces and mechanisms which contribute to the perpetuation of apartheid's legacy of poverty and inequality.     

How noise matters

Recent advances in evolutionary game theory have introduced noise into decisionmaking to select in favor of certain equilibria in coordination games. Noisy decisionmaking is justified on bounded rationality grounds, and consequently the sources of noise are left unmodelled. This methodological approach can only be successful if the results do not depend too much on the nature of the noise process. This paper investigates invariance to noise of these results, both for the random matching paradigm that has characterized much of the recent literature and for a larger class of two-strategy population games where payoffs may vary non-linearly with the distribution of strategies among the population. Several parametrizations of noise reduction are investigated. The results show that a symmetry property of the noise process and, in the case of non-linear payoffs, bounds on the asymmetry of the payoff functions suffice to preserve the known stochastic stability results.     

Conditional distributions of earnings,wages and hours for blacks and whites

This paper provides new evidence on the conditional distributions of earnings, wages and hours for white and black males in the University of Michigan's Panel Study of Income Dynamics. Conditional hours and ln wages are approximately normal for both races. Conditional earnings are approximately normal for blacks while earnings are well approximated for whites by the product of normal hours and log-normal wages. The distribution of this product is derived here for the first time. Treating the marginal earnings distribution as the average of the conditional distributions, we use these results to predict poverty and affluence rates in our sample.     

INTRAHOUSEHOLD INEQUALITY AT DIFFERENT WELFARE LEVELS: ENERGY INTAKE AND ENERGY EXPENDITURE DATA FROM THE PHILIPPINES*

ABSTRACTS This paper investigates the relationship between intrahousehold inequality and levels of household welfare. Under certain conditions it is demonstrated — with both the unitary model of the household and with some collective models — that the relationship between household welfare and inequality within the household can have an inverted u-shape. Using two sets of calorie adequacy data from a sample of 455 households in the Philippines, a spline analysis is used to test the hypothesis that inequality within the household first increases and then decreases as per capita household total expenditure increases. The two sets of calorie adequacy data are based on repeated 24- hour recalls of dietary intake, and on calorie requirements that are unadjusted and then adjusted for individual activity patterns. Results indicate that once activity patterns are accounted for, calorie intake shortfalls are borne fairly equally within the household at all per capita household total expenditure levels.     

Optimal maintenance center inventories for fault-tolerant repairable systems

In many military and commercial contexts, complex equipment which is expected to perform very reliably is often designed to be fault-tolerant, that is, able to function although some of the parts have failed. A popular fault-tolerant design is the m-out-of-n system, where there are n identical parts, at least m of which must be functional for machine operation. Complex equipment of this type often undergoes scheduled maintenance overhauls at regular intervals during which all failed components are replaced. Failure to have replacements on hand for failed parts requires emergency measures at premium cost. When repairable parts are highly reliable and expensive, both holding and shortage costs are high. A reasonable objective is to choose initial spares inventory to minimize the sum of holding costs and expected shortage costs.We first develop a model to determine the optimal repairable parts inventory for a maintenance center servicing machines containing a single m-out-of-n system. The model is then extended to handle a related problem, finding optimal maintenance center inventories for machines containing several m-out-of-n systems of different parts, minimizing total expected costs subject to a constraint on total inventory investment.We assume that there is a fleet of machines, which experience identical workloads. There is a cycle time of T days between overhauls for an individual machine. A machine arrives at the maintenance center for overhaul each day. At the overhaul, all failed parts are removed and sent to a repair shop, from which they eventually return to the maintenance center to be used again as spares. The total number of spares undergoing repair and on hand is a constant. There are no backorders; if the number on-hand spares is insufficient to meet demand at an overhaul, a shortage penalty is assessed which depends on the number and type of spares required.While computing holding costs is straightforward, computing expected shortage costs is more complex. Expected shortage costs are dependent upon several factors, including component failure rates, the values of m and n, part repair rates, and the initial number of spares on hand. We assume that the system of interest is well specified, so that the parameters of the model are known except for the number of initial spares of each type, which are the decision variables. We model the on-hand inventory of each type of part as a Markov chain with the number of spares on hand at the end of each day as the states, under the assumptions that failure rates are constant and repair times follow independent exponential distributions. We then calculate the steady-state probabilities of stockout of various numbers of spares, as a function of the initial spares inventory. The expected shortage costs for a given type of spare may then be calculated by finding the product of the penalty cost for lacking p spares and the probability of lacking p spares and summing over all possible p values.Solutions to the problem of finding optimal initial inventory level for a machine containing a single m-out-of-n system may be found easily by enumeration. Solutions to the constrained problem where the machine contains several independent m-out-of-n systems, may be found by dynamic programming. Sensitivity analysis of costs to changes in the inventory investment constraint is clear, and computational effort is reasonable. A simple example is included to illustrate the solution method for both problems.     

Vested Interests Oppose Consumers

Earlier attempts to overhaul the funding of education foundered in the face opposition from vested interests. Lawrence Norcross, Headmaster of Highbury Grove School in North London, warns that the educators will themselves require education if change is to be effective.     

THE APPLICATION OF ANALYSIS OF VARIANCE TO INTER-FIRM COMPARISON RATIOS

There is a lack of consensus about the utility and validity of information provided through firms participating in an Interfirm Comparison (IFC). The disagreement is a result of different notions about the purpose served by IFC schemes. The unresolved question is how to use the same information for two purposes - the appraisal of operating efficiency and the guidance of longer-term planning decisions. The application of analysis of variance to the results of an IFC helps to clarify the nature, and improve the utility, of the comparative data by identifying factors accounting for variation in performance among firms grouped by multiple characteristics.     

On the choice of immediate monetary targets

This paper studies the control problem of a stochastic monetary system. The Central Bank has the choice of two targets: the size of its portfolio of assets or the level of interest rate on that class of assets. If its objective is to minimize the variance of a monetary aggregate or of private sector interest rate, the conditions under which one or the other of the targets should be used are analyzed. However, if the ultimate objective is a minimum variance in a desired GNP level the effect of the immediate target is the same whether the central bank employs a money stock or a private interest rate target.