Several general themes emerge from the discussion, including:
• No single instrument is clearly superior along all the dimensions relevant to policy
choice; even the ranking along a single dimension often depends on the circumstances
involved.
• Significant trade-offs arise in the choice of instrument. In particular, assuring a reasonable
degree of fairness in the distribution of impacts, or ensuring political feasibility,
often will require a sacrifice of cost-effectiveness.
• It is sometimes desirable to design hybrid instruments that combine features of various
instruments in their “pure” form.
• For many pollution problems, more than one market failure may be involved, which
may justify (on efficiency grounds, at least) employing more than one instrument.
• Potential interactionsamongenvironmental policy instruments are a matter of concern,
as are possible adverse interactions between policies simultaneously pursued by separate
jurisdictions.