"In cooperation with the IPD the ROZ - the Dutch real estate umbrella organization - developed a long term index covering the period 1976 ñ 2003. Because the original ROZ/IPD-index started as late as 1995, the information related to the earlier years had to be constructed due to lack of historical data. The researchers acknowledged that the so gathered information is not fully reliable. From their point of views ""anything is better than nothing"", however, that's not in every case a good point of departure ñ as it is in this situation. The problem is that the so constructed long term-index in a short time enjoyed such a huge positive image, that the governmental branch supervisor has prescribed the use of it for Asset Liability Studies. The dubious reliability of the information on which the index is based, causes the return/risk-profile to show a too high level of risk. This is due to the stable course of the direct return vs. the volatility of the indirect return ñ and therefore of the total rate of return. The research attempts to solve that problem and an alternative approach is suggested. That might also be of interest for those real estate markets which, like the Dutch, don't have reliable long term historical data. "