It forces us to examine and evaluate critically the data that are
available; it prevents us from jumping to conclusions based on these
inadequate data; it reduces the loss and waste of time involved in
mechanical manipulations of the type represented by Pareto-curve-fitting to groups of data whose meaning, in terms of income concept,
unit of observation, and proportion of the total universe covered, remains distressingly vague; and most important of all, it propels us
toward a deliberate construction of testable bridges between the available data and the income structure that is the real focus of our interest.