the market"; as a result, no such market benchmarks could exist. Another commonly used, market-based approach to valuation is the capi- talization of the utility's earnings. Brandeis correctly pointed out, however, that capitalizing earnings necessarily embroiled regulatory authorities in a "vicious cir- cle," because the rate would depend on the utility's earnings, and the earnings were largely determined by the rates the utility was permitted to charge. The principal question confronting Brandeis was whether the rate base should be calculated based on historical cost or replacement cost. Brandeis recognized that replacement cost might well represent the best evidence of present value, because replacement cost constituted a better reflection of changes in demand and technol- ogy. In the end, however, pragmatic considerations led Brandeis to advocate relying on historical costs. Determining replacement cost was an inherently speculative endeavor fraught with uncertainty. In addition, basing value on replacement cost would expose both consumers and investors to the risks associated with fluctuations in market prices. In comparison, relying on historic cost allowed less subjective and less variable determinations of value. Although shifts in demand and technological obsolescence could cause replacement cost to overstate or understate market value in some circumstances, in the absence of data based on actual transactions, replace- ment cost remained a useful proxy (262 U.S. at 292-308). 14 Brandeis's analysis 13 The seminal case on the filed rate doctrine is Louisville & Nashville Railroad V. Maxwell, 237 U.S. 94 (1915). For a modern reaffirmation in the context of telecommunications, see AT&T V. Central Office Telephone, Inc., 524 U.S. 214 (1998). 14 To the extent that Brandeis's opinion evinces a strong desire to insulate both consumers and investors from the dislocation caused by market fluctuations, it exhibits some strikingly antieco- nomic tendencies. His preference for stability is perhaps explained by the de