A population census can be an example of a

A population census counts the whole population and, being repeated at fixed intervals, works as a longitudinal study tracking change over time.

Repetition every ten years yields comparable data across successive periods, the hallmark of longitudinal design.

Historical study relies on past records and relics rather than a live enumeration of living people.

Case study intensively probes a single unit, whereas a census covers the entire population.

Experimental study manipulates variables under control, which a descriptive census never does.

India's decennial census has run since 1881, giving one of the longest such data series.