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C H A P T E R O N E
Subtractability of use
Difficulty of
excluding
potential
beneficiaries
Low
High
Low
Toll goods
Private goods
High
Public goods
Common-pool resources
Figure 1.3 Four basic types of goods. Source: Adapted from V. Ostrom and
E. Ostrom 1977, 12.
from a finite total amount available for harvesting (E. Ostrom, Gardner,
and Walker 1994; Aggarwal and Dupont 1999). When a fisher harvests
a ton of fish, those fish are not available to any other fisher.
EXCLUDABILITY AND THE FREE-RIDER PROBLEM
When the benefits of a good are available to a group, whether or not
members of the group contribute to the provision of the good, that good
is characterized by problems of excludability. Where exclusion is costly,
those wishing to provide a good or service face a potential free-rider or
collective-action problem (Olson 1965). Individuals who gain from the
maintenance of an irrigation system, for example, may not wish to con-
tribute labor or taxes to maintenance activities, hoping that others will
bear the burden. This is not to say that all individuals will free-ride when-
ever they can. A strong incentive exists to be a free-rider in all situations
where potential beneficiaries cannot easily be excluded for failing to con-
tribute to the provision of a good or service.
When it is costly to exclude individuals from enjoying benefits from an
investment, private, profit-seeking entrepreneurs, who must recoup their
investments through quid pro quo exchanges, have few incentives to pro-
vide such services on their own initiative. Excludability problems can thus
lead to the problem of free-riding, which in turn leads to underinvestment
in capital and its maintenance.
Public sector provision of common-pool resources or infrastructure
facilities raises additional problems in determining preferences and or-
ganizing finances. When exclusion is low cost to the supplier, preferences
are revealed as a result of many quid pro quo transactions. Producers
learn about preferences through the consumers’ willingness to pay for
various goods offered for sale. Where exclusion is difficult, designing
mechanisms that honestly reflect beneficiaries’ preferences and their will-
25
D I V E R S I T Y A N D S T R U C T U R E D I N T E R A C T I O N S
ingness to pay is challenging, regardless of whether the providing unit is
organized in the public or the private sphere. In very small groups, those
affected are usually able to discuss their preferences and constraints on a
face-to-face basis and to reach a rough consensus. In larger groups, deci-
sions about infrastructure are apt to be made through mechanisms such
as voting or the delegation of authority to public officials. The extensive
literature on voting systems demonstrates how difficult it is to translate
individual preferences into collective choices that adequately reflect indi-
vidual views (Arrow 1951; Monroe forthcoming).
Another attribute of some goods with excludability problems is that
once they are provided, consumers may have no choice whatsoever as to
whether they will consume. An example is the public spraying of insects.
If an individual does not want this public service to be provided, there
are even stronger incentives not to comply with a general tax levy. Thus,
compliance with a broad financing instrument may, in turn, depend upon
the legitimacy of the public-choice mechanism used to make provision
decisions.
SUBTRACTABILITY
Goods and facilities can generate a flow of services that range from being
fully subtractable upon consumption by one user to another extreme
where consumption by one does not subtract from the flow of services
available to others. The withdrawal of a quantity of water from an irriga-
tion canal by one farmer means that there is that much less water for
anyone else to use. Most agricultural uses of water are fully subtractive,
whereas many other uses of water—such as for power generation or navi-
gation—are not. Most of the water that passes through a turbine to gener-
ate power, for instance, can be used again downstream. When the use of
a flow of services by one individual subtracts from what is available to
others and when the flow is scarce relative to demand, users will be
tempted to try to obtain as much as they can of the flow for fear that it
will not be available later.
Effective rules are required if scarce, fully subtractive service flows are
to be allocated in a productive way (E. Ostrom, Gardner, and Walker
1994). Charging prices for subtractive services obviously constitutes one
such allocation mechanism. Sometimes, however, it is not feasible to price
services. In these instances, some individuals will be able to grab consider-
ably more of the subtractive services than others, thereby leading to non-
economic uses of the flow and high levels of conflict among users.
Allocation rules also affect the incentives of users to maintain a system.
Farmers located at the tail end of an irrigation system that lacks effective
allocation rules have little motivation to contribute to the maintenance