italization are only as reliable as the data upon which they are based. For exam- ple, projections of future income are typically based upon a particular property's past earnings. Although such data are often reliable indicators of future earnings, at times they may fail to reflect the full range of technological and economic developments. 39 In addition, the Court has suggested that in the absence of better measures of value, courts can appropriately consider replacement cost when determining whether the government has provided just compensation (Kimball Laundry, 338 U.S. at 5-7). As noted earlier, replacement cost is better than historic cost at reflecting changes in value over time. Replacement cost also provides a useful price ceiling, because all those who purchase access can create the input themselves. At the same time, the Court's takings decisions recognize that replacement-cost approaches to valuation suffer from several conceptual limitations. First and foremost, such approaches do not necessarily reflect exchange value. 40 In addition, by failing incorporate any element that reflects demand, the replacement-cost approach may fail to account for technological obsolescence and thus may require compensation even "when no one would think of reproducing the property."4 Moreover, in order to compensate for functional obsolescence, courts must analyze the replacement cost of an equally efficient plant by allowing for physical depreciation. Failing to do SO would bestow a windfall on the property owner due to the difference in quality between the replacement facility and the older facility. Factoring in depreciation does, however, add considerable uncertainty to the valuation process. The Court reserved its heaviest criticism for historical cost, the valuation approach upon which authorities have relied most often when regulating network industries. 43 As the Court explained in United States V. Toronto, Hamilton & Buffalo Navigation Co., historical cost all too often represents a "false standard of the past" 