Several different depreciation systems may be used for group depreciation. The vintage group procedure treats the same type of property placed in service during the same year as a distinct group for depreciation purposes; therefore an estimate of the probable average service life and net salvage ratio(s) of each individual vintage is necessary. The vintage group procedure calculates an accrual rate for each vintage and the accrual rate for an account for specific calendar year is the weighted average vintage accrual rate for that calendar year. A further refinement would be to divide each vintage into groups such that all of the dollars in a group have the same estimated life-an equal life group (ELG). Then each ELG is depreciated over its estimated life. The effect is to recover each dollar over the estimated number of years it is in service. Each vintage is divided into several equal life groups (ELGs) such that all the property in a specific ELG has the same estimated life. The accrual rate for each ELG is based on the estimated life of that ELG. The vintage accrual rate for a specific year is the weighted average ELG accrual rate for that calendar year. In this paper, we illustrate the calculations of vintage accrual rates for each of the calendar years by the ELG depreciation systems.

When the number of items of same type of industrial property is quite large, calculating depreciation for a group of such items may be more efficient than depreciating each item separately. Several different depreciation systems may be used for group depr