In other fields cost benefit analysis has been used to compare the monetary costs with the monetary gains. If the gains are greater than the costs, the activity is worth financing. Where this has been applied to health services, the costs have been compared with monetary gains calculated in terms of earnings foregone with the comings in future years discounted to current values. Costs can include the costs of treatment, travel costs and costs to the patient in the time used to receive treatment. The rationale for discounting is that people place a higher value on benefits this year than in the future. Sometimes an allowance has been made for the value of the unpaid «work» of caring for dependent persons (e.g. children) and for housework. How to value the latter is controversial and it is hard to cost time for someone who is not in paid work, for example the unemployed, the elderly and children. Putting a monetary value on the real or potential gains of treatment is equally controversial and requires value judgements which may not be acceptable to the public at large.
Similarly, there is no «right» answer on the interest rate to choose for discounting future earnings to current values and such calculations are very sensitive to such choices.
Calculations can be made in terms of costs to the patient or the government or society as a whole. The latter would include expenditure on social welfare and social security payments and reductions in income tax as well the cost of publicly financed health care. This method expressly assumes that the value of each individual's life consists simply in the earnings that individual is commanding. The losses to society may be different from lost earnings if work can be postponed or a worker readily replaced from those unemployed. The retired, those with no jobs and no prospect of obtaining work because of disability or lack of skill have no value at all. Treatments which leave the disabled still too disabled to work are not worth financing. The results are inevitably biased towards the healthy and the more skilled young.