An impact evaluation consists of gathering and weighing evidence to determine the impact of products, programs, or projects upon a population affected by a set of actions designed to change the status quo. These evaluations may be used to draw evidence-based conclusions on whether introducing a change generates a positive or negative effect. An impact evaluation may calculate the average impact of change on individual users or clients, or may instead measure the overall benefits conferred upon a group of people collectively. Measuring these impacts may help governmental agencies, businesses, or charities more effectively utilize resources.
The first step in the process of conducting an impact evaluation is to determine the existing state of affairs. This step usually occurs before a change is undertaken, in order to more accurately gauge the post-change status. After the change has been implemented, the next step is to measure the impact or impacts. Both anticipated and unexpected impacts are subsequently noted and analyzed.
For example, an effort to provide government-sponsored free meals to needy children may be undertaken to improve children's health. Vouchers for nutritious food may be given to the children's parents. When the impact evaluation is subsequently assessed, researchers may find that the target population's health did not improve as much as was anticipated. Further investigation may reveal that the children's caretakers had devised a bartering system, in which the parents were trading meal vouchers for other essential non-food items, such as clothing or diapers.
As a result of the findings, the program evaluation revealed that the children's health benefits were not as significant as the voucher program's creators had hoped they would be. This is an example of measuring an impact on a defined set of specific individuals. A study of mortality rates from smoking cigarettes before and after banning cigarette advertising would be an illustration of measuring the collective impact of the ban upon a specific set of people who all use tobacco products.
An impact study may focus on consumer products as well. Marketing researchers may attempt to estimate how receptive consumers will be to a new product, based on similar product introductions by a company in the past. A researcher may also focus an impact evaluation on determining how a product may be used or what kind of consumer might be most likely to use it. Sometimes, an impact evaluation will yield unexpected results, demonstrating that the actual introduction of new practices or products may differ significantly from expectations. Impact evaluations are used by many organizations and businesses, and are considered to be a form of empirical evidence.