The future plays an important role in most human activities. In economics it is no different, for the economic actions of today are the basis for the economic fortunes or disasters of tomorrow. Yet, most economic actions are taken based on a perception of the future that is not known ahead of time. Therefore, decisions are made and actions are taken in anticipation of an uncertain future. Neither of these uncertainties is measurable.
True uncertainty is incapable of quantification and insurability.
Thus, it cannot be included in a model easily, without making subjective valuations of how economic participants respond to disappointing expectations about the future. In a world with true uncertainty, economic participants must remain more liquid in anticipation of disappointments down the road. Segmentation is based on the assets' liquidity properties. Each of these can be measured. All events are known and can be assigned weights or probabilities that sum to 1.0, such that a definitive and calculable outcome is possible.