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Appendix A

Infant mortality (q0)

For Interim Life Tables covering the period year T to year T+2 inclusive, infant deaths at <4 weeks, 1-2 months, 3-5 months, 6-8 months and 9-11 months are summed separately for males and females over the three years T, T+1 and T+2. The ‘at risk’ population is then derived for each group from the monthly birth figures, separately for males and females, as follows (where BXxxT = Births in Month Xxx of calendar year T):

<4 weeks:


1-2 months:


3-5 months:


6-8 months:


9-11 months:


Each of the total groups of deaths is then divided by the appropriate at risk population calculated above and the results totalled to give q0.

The m0 shown in the life table is calculated from q0 using the formula:


By making assumptions for the average age of death for each of the periods used for the infant death calculation, a0 can be calculated. The assumed average ages at death are as follows:

Age at death Assumed average age at death (months) Notes
<4 weeks 0.2 Based on analysis of England and Wales data for deaths under 1 month
1-2 months 1.5  
3-5 months 4  
6-8 months 7  
9-11 months 10  
Content from the Office for National Statistics.
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