Article aims to stimulate thinking as to how we might produce timely and more reliable estimates of changes in the value of portfolios, price indices based on a portfolio of properties, and other aggregate measures of trends in property values. Argues that a traditional market value appraisal of each individual property may not be necessary or optimal when the objective is to value portfolios or get a leading indicator of shifts in market value at an aggregate level. Instead, it is more important to use a critical mass of current market data that captures systematic movements in property values. Although a traditional market value appraisal is always more likely to capture the unique unsystematic characteristics of an individual property, automated valuation methods using a database of valuation data may provide the best way to get real time interim updates of real estate portfolios and create more timely real estate indices. References. Figures. [TAKEN FROM JOURNAL HEADNOTE]