General Fertility Rate
This measure addresses the crude nature of the CBR by focusing on that section of the population at risk of having births – women aged 15-49.It is constructed as follows:
| General Fertility Rate = | births in a stated period |
| number of women aged 15 - 49 in the same period |
It can easily be constructed from vital registration, census or survey data and does not rely on exact ages (except at beginning and end of age range).
This measure is a step above the previous two measures and a potentially useful and reasonably accurate measure of fertility because the numerator and denominator are focused and well specified and the denominator is truly those at risk of producing the numerator.
The General Fertility Rate (GFR) has specific uses in certain circumstances when one wants to know a total number of births for all women in the fertile ages. An example would be in calculations of maternal mortality – see PAPP104_S01. But in general it is not widely used because it still suffers a disadvantage concerning the structure of the population – similar to the problem with the CBR although on a smaller scale.
This problem is that the fertile ages – nominally 15-49 years – is 35 years wide and so within that range there can be substantial differences in age structure between populations. Because fertility is concentrated at certain ages populations can appear to have different levels of fertility simply because they have different age structures between ages 15-49 years. For international or secular comparisons one wants to have a measure that is independent of age structure and the GFR is not quite there. We need to move on to the Total Fertility Rate and a precursor to that is the construction of Age-specific Fertility Rates.