LibAnswers

This is a publication that does not have either 'Iowa' or 'curves' in its title making it difficult to locate. The “Iowa Curves” publications provide tables of probable average life expectancy for capital assets. For example, an electric utility owns 1,000 utility poles which periodically need to be replaced. The Iowa Curves publications provide data the utility can use in estimating the average life of their utility poles.

This information was first published in 1935 and 1942 as Iowa State College Iowa Engineering Experiment Station Bulletin #125, #155, & #156. All three bulletins were authored by Robley Winfrey. Print copies of these publications can be found at call number TA1 Io8b in Parks Library.

Bulletin #125 (1935) “Statistical analysis of industrial property retirements.” [Reprinted in 1967].

• View on Hathi Trust (open access)

Bulletin #155 (1942) "Depreciation of group properties"

• View on HathiTrust (open access)

Bulletin #156 (1942) "Condition percent tables for depreciation of unit and group properties."

• View on HathiTrust (open access)

In 1978 John G. Russo validated the “Iowa curves” in his Ph.D. dissertation, "Revalidation of Iowa Type Survivor Curves." DOI: 10.31274/rtd-180813-1381 (open access and call number: ISU 1978 R921)

In 1980 John G. Russo and H.A. Cowles published an article in the Engineering Economist under the same title as Dr. Russo’s dissertation. The article and dissertation compare data from the original bulletins with a new set of curves developed by Dr. Russo in his Ph.D. research. The article can be found at DOI: 10.1080/00137918008902863 but is (only available to subscribers).