Life characteristics of physical property

The following pages present a method of calculating the mortality curve, the probable life curve, and the rate of renewals of particular examples and types of physical equipment. The method has been applied to 65 sets of original life data for property found in the following industries : water supply, telephone, telegraph, electric service, electric railway, steam railroad, agricultural implement and motor vehicle. Sine the 65 mortality curves presented show very similar characteristics, they were redrawn so that the age was expressed in present of average life, and grouped into 13 classes, from which 13 type characteristics curves were drawn. Mathematical equitations were developed for some of the 13 type frequency and all of the total renewal curves. Fundamental relationships of the various characteristics of both the original 65 curves and the 13 type curves are given in tabular and graphical form. The 13 type curves can be used as valuable aids in forecasting the probably future service lives of the individual items and of groups of items of different kinds of physical equipment.