Demand analysis in general needs to deal with two fundamental elements: the first is the necessary identification of timing and special differences and the second is the necessary separation of ability and willingness in personal consumption behavior. Only by taking both considerations into account and adopting portfolio theory as the analytical framework and tool, can demand be realistically explained. As a consequence, this study demonstrates that numerous demand issues, including the designing of a national improvement indicator of economic life, can all be reasonably studied.Keywords: demand, portfolio theory, improvement indicator of economic life different types of time frame to study consumption behavior: (i) the very short-term, where personal preferences, disposable incomes and incomes are all assumed to be constant in order to reflect the very short-term stability of consumption habits and income proceeds; (ii) the short-term, where only personal preferences can be allowed to vary;(iii) the long-term, where both personal preferences and disposable incomes can be allowed to vary; and (iv) the very long-term, where personal preferences, disposable incomes and incomes can all be allowed to vary. (Note 1) Moreover, in this study, savings or dis-savings will be taken for the sole purpose of making current or future consumption.Uncertainty is a peripheral problem immediately arising from this framework. Although j d Y , can be predetermined as the personal consumption budget, expressing it as an uncertain j d Y , is still necessary if the meaning of personal expenditures is also assumed. Accordingly, all related analyses must be performed under type (iii) or (iv) time frame, because personal disposable incomes can typically be allowed to vary only in the long-term. Moreover, by assuming www.sciedu Published by