Single word request: a non-changing temporal trend [closed]

Is there a word for describing a non-changing temporal trend? Stasis?

E.g. expenditure on health care did not change between 2000-2020.


So far as I can make any sense out of the given information, the word you seem to be looking for is constant.

INVARIABLE, UNIFORM

[Merriam-Webster]

So you could say Expenditure on healthcare remained constant during 2000-2020.