Longman Dictionary of Contemporary English
natural wastage
noun
EXAMPLES FROM CORPUS
▪ For the Army we are talking about in excess of 10,000 redundancies and much of the other reductions will occur through natural wastage.
▪ He didn't mind the natural wastage, at all.
▪ Membership from now on will be by invitation only as existing places become available through natural wastage.
▪ No, natural wastage, as they call it these days, took care of the decrease.
▪ Ten of the posts to go will disappear through natural wastage.
▪ There is a natural wastage of at least five percent on any diet.
▪ Voluntary redundancies and natural wastage are expected instead of sackings.
Wiktionary
natural wastage
n. (context British business English) Decrease of workforce caused by non-replacement of retiring or voluntarily resigning employees and not by deliberate layoffs.