Animal welfare can be hard to quantify, especially for the freedom to express normal behaviour, and the freedom from fear and distress. Output-based measures use animal-based measures in four areas: physiological response, health and injuries, production level, and behaviour. Usually, some combination of these categories is used, as just using one can give an inaccurate assessment. Input-based measures include resource and management-based measures, and can also be considered as they assess the environment and care from the stockperson. Animal-based measures tend to more accurately reflect the actual welfare of an animal, but input-based measures are easier to measure. One system to measure welfare is the European Welfare Quality Program, which puts livestock farms into one of four welfare categories. It scores the farm on the animal-based measures of good health, housing, feeding, and appropriate behaviour from 0-2, and then puts it in the category that corresponds to the points. Another system is the American PQA Plus Program, which is mainly uses input-based measures. It involves 12 practices for swine production, and evaluate 10 of them as acceptable or to develop and implement an action plan. The Canadian ACA Program started as a voluntary program, and is now required as part of the Canadian Quality Assurance program. It is under revision, but the current mandatory requirements are largely management-based. The three programs vary in their approach, but all help to quantify animal welfare and address when it is inadequate.