IN GEOMETRIC TERMS

situations are rare in practice, but they are certainly im-aginable and sometimes even occur. In such situations aman would be willing to save for the future without anyincentive in the form of interest. But this takes us be-yond our present point; for here we are concerned onlywith the Willingness lines, not with the Market lines.

§10. The Personal and Impersonal Influences onImpatience

By the aid of this map we can see, anew, and moreclearly, that a man’s actual degree of impatience dependson two circumstances:

(1) It depends on his “personal equation,” the wholecontour of his whole family of Willingness curves, repre-senting what he would be willing to do under all sorts ofincome situations. The Willingness lines of a spendthriftare steeper and those of a miser less steep than the typical,or normal, man’s family of curves.

(2) It depends on his particular income situation onthe map which is represented by the letter P. A poor manis more impatient than a rich man of the same personalcharacteristics. A man with great expectations for thefuture but with little available for the present is moreimpatient than the man oppositely situated with respectto the future.

Both the family of Willingness lines and the position onthe map are, of course, changing every minute. Only atone particular time does the map, with its set of curvesfor Individual 1, and a particular location P u picture hisindividual circumstances. What we are doing here is totake a flash-light, as it were, of his income situation andhis Willingness lines, and to analyze his behavior at theinstant.

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