PAPP101 - S04: Measuring fertility

Crude Birth Rate

This measure is a simple ratio of the number of births in a particular period (usually a year) divided by the total population size.

Crude Birth Rate =	births in a stated period
	mean population over that period

The denominator is technically the person-years lived in the year, but this is usually estimated as the mid-period population, which is itself estimated as the mean of the population at start and end of the period.

The CBR is commonly quoted per 1,000 population.

It is a measure well suited to construction from vital registration providing the numerator and census data providing the denominator. As such it is easily and accurately calculated in developed countries with well-developed vital registration systems and good census data. It is less well estimated from survey data , although it can be done.

The denominator needs to be an average population size for the period concerned and this is often estimated as a mid-year population – that is the average of the population at the start of the period and at the end of the period.

Please answer the questions on the following pages.