Regulation of public utilities in the form in which we know it today is a development of the past fifteen years. The New York and Wisconsin laws in 1907 practically mark the beginning of present methods of regulation. Under these and other laws passed since that time regulation has become less and less a matter of bargaining and of local politics and has come to be more and more a matter of fitting the requirements of regulation to the cost of doing the business. Among these costs that of meeting the loss occasioned by the retirement of property has been by no means the least important. A literature all its own has grown up around the subjects of depreciation, the physical phenomenon, its causes, and the importance of provision for it. Much that was written on the subject was evidently the result of a decidedly imperfect understanding, both of the physical questions involved and of its financial and accounting aspects. I will not attempt to do more than speak briefly of some aspects of the accounting problem.
Pennsylvania. Department of Public Instruction, "Depreciation" (1922). State Publications. 68.