Incidence is the number of new cases diagnosed in a given period in a given population. It can be expressed as an absolute number, as a rate per a certain number of population, or as a rate per a certain number of population after age standardisation.
Crude incidence is the number of new cases arising per 1 million persons in a given population; depending on the context, the number of persons is equal to the entire population of children and adolescents aged 0–19 years, children aged 0–14 years, adolescents aged 15–19 years, only boys or only girls in a given age group.
Age-standardised incidence rate (ASR) is the weighted mean of crude incidence rates in age categories, with weights of crude rates in individual age categories being proportional to the number of persons in a standard population. In other words, ASR is the number of new cases per 1 million persons if the population of interest had the same age structure as the standard population. Either the European standard population (E)  or the world standard population (W)  are generally used in calculations, i.e. theoretical populations for which the percentages of persons in individual age categories approximately correspond to a given real population.
- Revision of the European Standard Population – Report of Eurostat’s task force – 2013 edition. Publications Office of the European Union, Luxembourg 2013. ISBN 978-92-79-31094-2. doi: 10.2785/11470
- Doll R, Payne P, Waterhouse JAH (eds.): Cancer incidence in five continents, Vol. 1. Union Internationale Contre le Cancer, Geneva 1966.