Optimal Time Allocation Research Articles

Diffusion and Adoption of Crops in Evolutionary Perspective

Optimization models developed within evolutionary ecology provide a useful framework for analyzing patterns of acceptance and utilization of new crops by food-producing populations. The deterministic version of the diet choice model predicts that new crops of relatively low profitability are likely to enter the diet if highly ranked resources are in short supply, but will be ignored if such items are abundant. A stochastic version of the same model (the “zscore” model) predicts adoption when the chance of energetic shortfall is very low and addition of new foods (even if they are of poor quality) may minimize risk by reducing variance in yields. Similar environments may consequently elicit strikingly different responses to new resources depending on which goal (e.g., risk minimization or efficiency maximization) guides decision-making. A case study, the introduction of the peach to eastern North America, illustrates how these models might be enlisted to develop and evaluate adaptation-based explanations of crop adoption. The opportunity cost model is used to predict optimal time allocation to different tasks as a function of the relationship between rising opportunity costs and diminishing returns. Manipulation of the model suggests that high opportunity costs may have limited investment in maize production following the initial introduction of this crop to eastern North America. Both increased productivity of maize and improvement in labor efficiency are likely causes of its eventual establishment as an economic staple. These findings illustrate the heuristic value of evolutionary ecology models as tools for investigating the origins and development of agricultural systems, including the diffusion of specific crops.

Optimal allocation of test positions and testing time in a factorial life testing experiment

This paper describes how to plan an “optimal” life testing experiment when the lifetime is assumed to have an exponential distribution. We further assume that the mean lifetime is equal to exp( β 1 x 1 + ⋯ + β k x k ) where the covariates x i form an orthogonal Hademard-type matrix reflecting the testing conditions, and β i are the unknown parameters. There are n 0 testing positions available, each one during the time interval [0, t 0]. This interval is divided into k stages of length t i , i = 1, … , k, and on each of these stages all devices operate under a fixed testing regime. Each device which fails is immediately restored and continues to operate. A closed maximum likelihood solution is given for estimates of β i . An expression for ΣAsVar[β̌ i ] is derived, which serves for obtaining an approximate optimal duration of the ith testing stage, t i ∗ . It is shown that t i ∗ is proportional to the square root of the mean lifetime for the corresponding testing regime.

Sustained vigilance and animal performance

Psychological studies have established that the central nervous system cannot sustain vigilance for an extended period of time. The consequent vigilance decrement implies a gradual reduction in the ability to process information effectively. This may result in a reduced ability to detect hidden predators, locate cryptic food items or make successful behavioural decisions. A model incorporating parameters of vigilance decrement during foraging and vigilance recovery during rest predicts first, the optimal allocation of time between foraging activity and rest, and second, the optimal length of each foraging episode. For a given rate of vigilance recovery, the model predicts that both the optimal proportion of time devoted for foraging activity and the optimal length of a foraging bout should be decreasing functions of the rate of vigilance decrement. Because the rate of vigilance decrement is larger for more difficult tasks, both the total time spent foraging and the duration of each foraging episode should be smaller for more demanding foraging activities. It is suggested that vigilance decrement is a dominant factor determining temporal patterns of animal behaviour.

Optimal allocation of assessment time in randomized pretest-posttest designs.

The widely used pretest-posttest design traditionally consists of a pretest and a posttest of equal lengths. However, greater statistical power can usually be achieved by using a posttest that is somewhat longer than the pretest. This article provides a method for calculating the optimal allocation of pretest and posttest assessment units so as to maximize power and presents the accompanying reduction in required sample size for a range of parameter values. When insufficient information is available to estimate the optimal allocation precisely, the effects of allocating 75% of the assessment units to the posttest are evaluated

Optimal allocation of time in a hospital pharmacy using goal programming

This paper presents a preemptive goal programming model for optimal allocation of personnel time among various tasks in a hospital pharmacy. The model assigns priorities based on daily time intervals, and ensures that the incomplete tasks belonging to the time interval under consideration are fully satisfied in the next interval. We apply the goal programming model to a situation involving a large hospital pharmacy and make a recommendation regarding its staffing requirements.

Pilots learning time evaluation under cost constraints

The purpose of this paper is to present a model for optimizing man-machine system reliability under resource constraints, taking into account the interactions between humans and hardware subsystems. The optimal learning time allocation for pilots is determined both by minimizing the expected total cost and by satisfying a man-machine system reliability objective. A numerical example has been considered: the fulfilment of an aircraft trajectory changing mission (ordered from the ground) by a two-pilot crew with maximum probability, taking into account the aircraft hardware system, the skill of the pilots and finally the interaction between pilots and aircraft.

Optimal consumption, training, working time, and leisure over the life cycle

In this paper, we analyze the joint determination of optimal consumption and allocation of time between learning (accumulation of human capital), working for wages (used for consumption and accumulation of financial capital), and leisure. Using Hopf bifurcation theory, we are able to show that cyclical training, working, leisuring, and consumption are optimal under certain constellations of parameters.

The optimal allocation of time during the diving cycle

The optimal allocation of time during the diving cycle

Optimal Allocation of Time and Estimation of Market Wage Functions

Second-generation studies of wage determination are based on the observation that wages of employed workers are a biased sample of the true population values because of selectivity, and a well-known two-stage method to correct for selectivity bias has been proposed by Heckman (1976). The basic notion behind the second-generation approach is that, in a setting of optimal decision making, the individual's choice of market work or not conveys valuable information that can improve our ability to estimate market wage equations. In this paper, we extend second-generation studies by proposing that there is additional useful information for estimating market wage functions in knowing not only if participation occurs, but also knowing how many hours a person actually works in a household sector (as opposed to consuming pure leisure). Accordingly, we extend the conventional work-leisure model of labor supply to accommodate time devoted to household production and adopt an estimation technique that addresses simultaneously the issues of sample censoring and the joint determination of nonmarket returns and nonmarket time. It appears that the disentanglement of the effects of investments in human capital on market and nonmarket productivity lead to sizably higher labor market returns to schooling, tenure, and experience for women than those obtained by standard approaches.

The deterrent effect reconsidered: The minimum-time approach

This article reconsiders the deterrent effect in the economics of crime according to Becker-Ehrlich's model of optimal allocation of time under uncertainty. In a particular group of crime suppliers, we can think of a certain type of individuals who are concerned with the minimum time allocated to illegal activities. Thus, our analysis is closer in spirit to that of insurance under conditions of risk. It is proved that the aforementioned individuals will increase the minimum time allocated to illegal activities when the subjective probability of apprehension exogenously increases. Some empirical estimates of larceny, in Japan are provided.

A simultaneous equation model of spousal time allocation

Given the complexity of spousal arrangements regarding market work and housework that have emerged during the last decade, time allocation by an individual within a family unit can no longer be treated as independent; albeit joint spousal decision making has not been properly modeled in the time-allocation literature. Accordingly, we develop a theoretical model which explains optimal time allocation of a typical dual-earner household which accounts for both interindividual and interactivity simultaneity. The model is estimated using a full information maximum likelihood technique with data from the 1983 wave of the Panel Study of Income Dynamics. While this study improves on prior work in the area of time allocation by taking interdependency and interactivity simultaneity into account, many of the findings are consistent with those of previous studies where allocation decisions have been assumed to be independent. Modeling spousal decisions jointly and correctly, however, should serve to narrow the gap between theory and actual time-allocation behavior.

4847810 Memory having redundancy circuit

The purpose of this paper is to present a model for optimizing man-machine system reliability under resource constraints, taking into account the interactions between humans and hardware subsystems. The optimal learning time allocation for pilots is determined both by minimizing the expected total cost and by satisfying a man-machine system reliability objective. A numerical example has been considered: the fulfilment of an aircraft trajectory changing mission (ordered from the ground) by a two-pilot crew with maximum probability, taking into account the aircraft hardware system, the skill of the pilots and finally the interaction between pilots and aircraft.

Stochastic unpaced line design: A reply

Executive SummaryIn the May 1985 issue of the Journal of Operations Management, we published a paper containing two major segments (Smunt and Perkins (1985)). The first segment provided a comprehensive review of previously published research on unpaced assembly lines. Two of the primary references in this review were path‐breaking studies by Hillier and Boling (1966) and Hillier and Boling (1979). These studies introduced the idea of the “bowl phenomenon,” which suggests that line output can be increased (compared to a balanced line) by unbalancing the line with high service times placed at the beginning and end of the line and low service times placed in the middle of the line. This pair of studies also verified the existence of the bowl phenomenon for exponential and Erlang service times with line lengths up to five stations and buffer capacities between stations from zero to four units.The second segment of our 1985 paper reported on a set of experiments to investigate the “robustness” of the bowl phenomenon under varying service time and buffer capacity assumptions. We tested and confirmed three primary hypotheses: The use of the bowl distribution to unbalance an assembly line will not significantly increase the output rate as compared to a balanced configuration when normally‐distributed work station service times are employed with less variance than the exponential distribution. Minimal increases of buffer storage capacity will significantly reduce or will negate the benefit of using the bowl distribution. Output rate is not highly sensitive to moderate variations from optimal task time allocation for stochastic unpaced lines.In other words, we found that the bowl distribution does not have advantages over a balanced line if either more realistic normally‐distributed service times are used or larger buffer capacities are available. Thus the bowl phenomenon, while interesting, does not appear to exist in most real world unpaced lines.In the “Note” which immediately precedes this “Reply,” the authors take issue with our conclusions, based primarily on their view that our 1985 experiments were “flawed.” While the “Note” authors provide some valuable arguments and correctly point out a weakness concerning the number of simulation repetitions in our 1985 study, in general it is their arguments that are “flawed,” as we will establish in this paper. In responding to the preceding “Note,” we have conducted a very extensive simulation experiment—much larger than either our 1985 study or the small study conducted as part of the preceding paper. The results of this enhanced study provide strong support for the conclusions of our 1985 paper.

Foraging Behaviour of Japanese Monkeys: a viewpoint of optimal foraging strategy

Most of the situations to which optimal foraging theory has been applied can be divided into the following four categories: (1) optimal food choice; (2) optimal food patch choice; (3) optimal time allocation to different food patches; (4) optimal patterns and speed of movements (Pyke et al., 1977). I have reviewed the ways in which the first three problems have been tackled thus far in primate feeding ecology. I have also reconsidered the foraging behaviour of the wild Japanese monkeys that inhabit Kinkazan Island, Miyagi Prefecture, in terms of net rate of energy intake which is usually employed as a measure in analyses of optimal foraging theory. I found that there was no significant tendency for the monkeys to spend more time in feeding on food items that are associated with more rapid energy intake. Furthermore, monkeys chose the higher-quality food patch (i. e., where the feeding speed was higher) and fed there, but showed no significant tendency to feed for a longer time in the higher-quality patch. I have discussed ecological factors other than the net rate of energy intake and social factors that influence these results. Finally, I have presented a summary of the general foraging strategies of Japanese monkeys that I have studied thus far.

What do agricultural income and productivity measurements really mean?

Statistical data on labour productivity and income in agriculture reveal large discrepancies between various EC member states, both with respect to their absolute levels and in relation to non-farm productivity and income in the respective countries. Insofar as they appear to reflect the failure of markets in allocating agricultural resources efficiently, and seem to be inconsistent with conventional wisdom concerning structural adjustment of agriculture, however, it can be seen that those data are misleading to a large extent. Based on a simple model of optimal time allocation between farm and non-farm activities of members of farm households, it is demonstrated that farm labour productivity and income must be different according to differences in the relation of farm to non-farm labour supply. The implications concerning international, interregional, intersectoral and intertemporal comparisons of income and productivity are discussed as well as the relevance of market failure in agriculture.

What do Agricultural Income and Productivity Measurements Really Mean?

AbstractStatistical data on labour productivity and income in agriculture reveal large discrepancies between various EC member states, both with respect to their absolute levels and in relation to non‐farm productivity and income in the respective countries. Insofar as they appear to reflect the failure of markets in allocating agricultural resources efficiently, and seem to be inconsistent with conventional wisdom concerning structural adjustment of agriculture, however, it can be seen that those data are misleading to a large extent. Based on a simple model of optimal time allocation between farm and non‐farm activities of members of farm households, it is demonstrated that farm labour productivity and income must be different according to differences in the relation of farm to non‐farm labour supply. The implications concerning international, interregional, intersectoral and intertemporal comparisons of income and productivity are discussed as well as the relevance of market failure in agriculture.

Science as a rational enterprise

Scientists often disagree about whether a new theory is better than the current theory. From this some (e.g., Thomas Kuhn) have inferred that the values of science are changing and subjective, and hence that science is an ‘irrational’ enterprise. As an alternative, this paper develops a ‘rational’ model of the scientific enterprise according to which the scope and elegance of theories are important elements in the scientist's utility function. The varied speed of acceptance of new theories by scientists can be explained in terms of the optimal allocation of time among different scientific activities. The model thus accounts for the ‘rationality’ of science in a way that is broadly consistent with the empirical evidence on the history and practice of science.

Sales Commission for Multiproduct Sales Forces

In the early 1970s several papers computed commission rates with the criterion that they be chosen so that the optimal time allocations for salesmen were the same as the optimal times for the firm. Recent papers have considered a principal-agent model for a single-product firm in which the firm sets commission rates knowing how the sales force will allocate time for any given rates. These papers assume that the probability distribution of sales is a function of sales effort. In this paper, we also consider a principal-agent model, but for deterministic sales of a multiproduct firm. A computational procedure is illustrated.

Labor, Work, and Leisure: Human Well-Being and the Optimal Allocation of Time

(1987). Labor, Work, and Leisure: Human Well-Being and the Optimal Allocation of Time. Journal of Economic Issues: Vol. 21, No. 1, pp. 167-188.

Working and selecting a retirement age: an optimal control approach

This paper examines how an individual can plan the optimal allocation of time to work activities and the optimal selection of a retirement age. The individual is assumed to divide his discretionary time into nonwork activities (for which he receives utility of leisure) and work activities. The wage that is earned during work is added to the stock of wealth that the individual accumulates for retirement. At retirement, the individual receives utility that is a function of the stock of wealth that he has been accumulating and his anticipated remaining life. Necessary and sufficient conditions are given for the optimal allocation of work activities for different utility functions. Numerical examples for these cases are also included.