Phyrr noted that one of the more complex issues regarding simulation of real estate cash flow returns
involved the uncertainties of the underlying input parameters. Multiple input variables with varying
degrees of correlated and uncorrelated probability distributions all contributed to return risk. To
generate an accurate model, probability distributions for each parameterized factor had to be known in
advance. As the author notes, determining these distributions required a skilled market analyst capable
of producing the underlying demographic and market-specific data needed to make such
measurements. The analyst also needed to be skilled in the various mainframe tools used to generate
the parameterized distributions. Most practitioners of the time had limited knowledge these more
advanced techniques.