The main principles of cost-benefit are encompassed within four key questions:
There is always uncertainty surrounding the estimates of future costs and benefits associated with a public investment project, and cost-benefit analysis needs to allow for this uncertainty by testing the sensitivity of the net benefits to changes in such factors as project life and interest rates. See WELFARE ECONOMICS, COST EFFECTIVENESS, TIME PREFERENCE, ENVIRONMENTAL AUDIT, VALUE FOR MONEY AUDIT, ENVIRONMENTAL IMPACT ASSESSMENT.
A decision-making tool that evaluates all the hard-dollar and economic consequence costs associated with pursuing a course of conduct against all the hard-dollar and economic consequence benefits reasonably to be expected from that decision,and comparing the two to see if they make economic sense.
Example: Riverdale Apartments is experiencing increased competition because of the abundance of new apartment projects being built nearby. In order to compete more effectively, it is considering adding a sophisticated security system with Web cameras allowing residents to monitor gate access; areas around the buildings; and common areas such as the laundry room, swimming pool, and playground. The hard costs of $270,000 can be partially defrayed by charging rental rates $15 per month higher than other properties. Spread across 200 apartments, this results in an additional income of $36,000 per year. In addition, the system is anticipated to result in the ability to retain occupancies at 95 percent rather than an expected short-term drop
to 75 percent until the new apartment buildings fill up and begin charging market rents in about 2 years. Calculations may attach a value of $36,000 per year to this consideration. Finally, the security system will result in significant insurance premium reductions amounting to $20,000 per year. The total short-term economic benefit is $92,000 per year for 2 years and $56,000 per year each year afterward (without adjusting for inflation or the cost of money). As a result, the initial $270,000 investment can be recouped in about 31/2 years and will show a profit afterward. After completing this cost-benefit approach, management will probably decide to spend the money for the improvements.