DEMAND AND VALUE 29

the available supply? What is the highest grade of utility
which fails to get satisfaction because of too keen competition
 for a limited supply? The value in exchange of the
commodity is too great for the latter, but not too great for
the former. If the grades of utility do not differ from each
other by considerable amounts, the two limits named will be
not far from identical. The measure of the exchange value
is, then, the utility which is on the margin of not being
realised, or the marginal utility.
When this marginal utility is small, the value in exchange
is small, however great the total utility of the commodity.
The more nearly our supplies of any commodity approach
the amount required for satiety, the smaller the marginal
utility, and the value in exchange to which it corresponds.
Thus, the more completely the resources of society are made
available for our well-being, the smaller is the measure of the
wealth they represent. If all our wants were supplied freely,
we could count none of the supplies among our wealth,
though, in a certain sense, our well-being would be far more
effectively secured than now. The increase of well-being is
certainly not inconsistent with a decrease of the exchange
value of the goods we enjoy. Yet the study of the sources
and modes of creation of wealth retains great importance.
It is very far from being true that decrease of wealth is
necessarily associated with increase of well-being. To have
a share in a large aggregate of wealth will generally enable
more wants to be satisfied than to have an equal proportionate
 share in a smaller aggregate. It is, further, of no
small importance to note that, in those lands where a
minimum of effort suffices to procure natural products
sufficient for the simplest needs of existence, the supply of
the means of meeting the more complex needs has not,
generally, reached a high level of abundance. Man is
induced to do little except under the stress of necessity, but
the development of his capacities, under that stress, puts him
in a position to command more that is worth having than
falls to him when the lavishness of nature encourages
indolence.
Changes in the demand for a commodity, as that phrase