On October 30, President Bush signed legislation
into law that makes it possible for recipients of
water from California's Central Valley Project to
resell that water. This legislation is controversial,
because it is expected to plant the seeds for the
development of a water market in California,
Among the most frequently cited objections to
using markets to allocate water are concerns that
the results would be unfair and disruptive: In particular,
opponents argue that a move to market
prices would mean a large shift in water from
farms to cities. This change in water allocation,
they argue, would lead to reduced agricultural
income and production, lower income in agriculturally
dependent communities, and higher
food prices. In the extreme, this stylized scenario
predicts a world with fountains in Beverly Hills
and desolation in California's central valley farming
region.
This vision of the distributional consequences of
a market system for water results, in part, from
putting together two statements about price determination
and drawing the wrong conclusion.
These statements are that (a) water is extremely
valuable, and (b) that the value of a commodity is
reflected in its price. Thus, the conclusion drawn
by some is that water prices would be high in a
market system and that low income and agricultural
consumers would be severely limited
in their abilities to purchase water.
This conclusion does not necessarily follow,
however. In fact, a similar debate took place in
the economics literature in the eighteenth and
nineteenth centuries before being put to rest by
Alfred Marshall. Known as the "Diamond-Water
paradox:' the issue sought to explain how the
observed price of water could be below that of
other commodities, such as diamonds, given
water's high value in sustaining life. Marshall's
solution to the paradox was to recognize that
prices reflect the value of the last, or marginal,
unit, not the value of all units consumed. He
demonstrated that a commodity that has high
value to society could have a low price if it
were available in sufficient supply.
As discussed in this Weekly Letter, this insight is
relevant to the current debate. The evidence sug~
gests that water markets would not lead to a high
price for water, because while urban users now
pay a significantly higher price than agricultural
users, that reflects differences invalues of the last
unit consumed by the two groups given artificial
restrictions on trading. In fact, the eyidence suggests
that water use patterns would not be affected
significantly, implying that the effects on agricurture
and agricultural communities would not be
large.
The paradox
The diamond-water paradox was puzzled over
for nearly a hundred years in the economics literature.
Adam Smith considered the issue in the
late eighteenth century, and David Ricardo spent
considerable effort trying to understand this
seemingly logical inconsistency with relative
price determination. Why would water, which
is essential to life, carry a price that is below that
of diamonds, whose use is far less critical?
Ricardo, the father of the labor theory of value,
tried to apply that theory to this case. He argued
that the cost of a commodity reflected the embedded
labor needed to bring that product to
market. Thus, he argued that water was relatively
cheap because it required less labor effort to
acquire than did diamonds.
While seeming to solve the dilemma, it was left
to Marshall to develop the correct answer to the
paradox. Marshall's answer can be seen in the
figure. Supply and demand curves for diamonds
(good 1) and water (good 2) are shown in the
two panels of the figure. As shown in the figure,
prices are determined where supply and demand
intersect in each market (points B and G), and
given the low quantity of diamonds, the equilibrium
price of diamonds exceeds that of water.
The important factor to note is that this is a marginal
condition. Prices measure the value of the
final unit consumed. The total value derived from
use is measured by the area under the demand
Figure 1
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