Doubts about these at the time the program began may provide clues for the diagnosis of later problems. The objectives of a program can often be subdivided to aid the evaluation. For example, if the goal were to increase book circulation the increase achieved in various categories could be measured. If more members were sought then the number of new adult, teen and child members could be measured. The success of the program in each category can then be rated on a scale such as exceptional, good, average, poor and unsatisfactory.
Evaluation is thus easier.
You can learn what you did to get some exceptional improvements and what you should have done to avoid the unsatisfactory. Just measuring total circulation increase or membership growth will reveal little and will not indicate where effort should be applied in any future campaign.