List any four characters that are employed in human population census.

The characters that are employed in human population census are:

- Natality and mortality – Natality (birth rate) is the production of new individual of any organisms per unit of population per unit time, mortality (death rate) is the rate of death of individuals per unit time.

- Sex ratio – it is the proportion of males to females in a given population, usually expressed as the number of males per 100 females at specific stage in life.

- Population density – It is the number of individuals of a species per unit area or space at a given time.

- Age distribution – It is the number or percentage of individuals in a population in different age group.