The most common trade-off is between money and a good or service received by some proportion of the citizenry, such as extending library hours from 8 p.m. till 10 p.m. weighed against a cost of $ 200,000 annually. Another common trade-off, especially in regulatory policies, involves weighing privately borne costs (a company’s installing pollution abatement equipment) against social benefits (improved health and the protection of forests).
Commensurability
Suppose some Alternative A1 stacks up very well on Criterion C1, moderately well on C2, and poorly on C3. And suppose that A2 stacks up in the opposite way. We can choose between the two alternatives only if we can weight the importance of the criteria and if we can express their relative weights in units that are commensurable