ISIC Rev.4 er en standard klassifikasjon av økonomisk aktiviteter ordnet slik at enheter kan bli klassifisert i henhold til den virksomheten som de er en del av. Kategoriene til ISIC på det mest detaljerte nivå (klasser) are delineated according to what is, in most countries, the customary combination of activities described in statistical units and considers the relative importance of the activities included in these classes. While ISIC Rev.4 continues to use criteria such as input, output and use of the products produced, more emphasis has been given to the character of the production process in defining and delineating ISIC classes.