olemus
statistikas: millegi (näiteks haiguse, kuriteo) esinemissagedus või populatsioonis mingil perioodil ilmnemise kordade arv

Wiktionary:
2. the extent or the relative frequency of something happening
5. (epidemiology) a measure of the rate of new occurrence of a given medical condition in a population within a specified period of time

ülevaateid
http://www.sjsu.edu/faculty/gerstman/hs161/pre-inc-key-points.PDF

https://www.statisticshowto.com/prevalence-in-statistics-incidence/

näiteid
https://ec.europa.eu/eurostat/statistics-explained/index.php?title=File:Fatal_accidents_at_work,_2015_and_2016_(standardised_incidence_rates_per_100_000_persons_employed)_AAW2019.png

https://en.wikipedia.org/wiki/Incidence_(epidemiology)