Decision analysis for determining the optimum planning horizon in aggregate production planning: Part 2: Difference between planning horizons in weekly and in monthly schedulings

Abstract

The effects of changing a unit time length of a planning horizon from a month to a week on the optimum planning horizon were examined by calculating the optimum planning horizon through the methods proposed by Nagasawa, Nishiyama, and Hitomi (1982). It was found that the optimum planning horizon decreased by 20-30% in calendar time when the unit time length was changed from a month (monthly scheduling) to a week (weekly scheduling). However, the degree of this decrease was much smaller than the (65% shown by Bernardo (1978), and it followed that the optimum planning horizon largely increased in the number of periods with this change of the unit time length. It was also clarified that the large amount of the decrease shown by Bernardo was derived on the basis of the erroneous analysis of the relation between cost coefficients and the unit time length. Consequently, weekly scheduling was not always preferred to monthly scheduling