Proggles per day, or PPD, is most commonly used as a metric of autism for legal or medical purposes. It is usually expressed as a frequency in terms of number of posts made at /prog/ in 24 hours. That is commonly expressed without units. Each country or state may define PPD differently. For example, the U.S. state of California defines their PPD as a ratio of autistic proggles per 100 regular proggles[1].