Single point in time
The term single point in time or snapshot is used to refer to situations where we want to calculate measures, or ratios of measures, that involve counts of entities (typically, counts of living populations and subpopulations) at a single point in time. We cannot use single point in time to calculate counts of events, because events can only be measured in a given measurement period (typically a year).
Ratios that make sense at a single point in time
Note that these ratios must have both their numerator and denominator as measuring counts of entities, typically, subpopulations of a given population.
Some examples are: