The total fertility rate (TFR), also known as the total period fertility rate, provides a single measure of fertility, by summing age-specific rates for each single year in the reproductive age range (11-49 years). The TFR represents the average number of children per woman that would be born to a group of women if current age-specific patterns of fertility persisted throughout their childbearing life.
The figures for 2001 to 2007 have been obtained from Office for National Statistics: Key Population and Vital Statistics, and for 2008 to 2011 from NHS Clinical and Health Outcomes Knowledge Base (search for "fertility").
Lancashire and national results
In 2011, the total fertility rate in England and Wales was 1.93 children per woman, which is below the so-called "replacement level fertility" (2.1). It is lower than the rates recorded between 2007 and 2010, but is well above the low point of 1.6 recorded in 2001. The current level of fertility is relatively high compared with that seen during the 1990s, but it was considerably higher during the 1960s 'baby boom' when the TFR peaked at 2.95 children per women in 1964.
Patterns of fertility in the Lancashire sub-region have largely followed those nationally, and in 2011 were virtually on a par with the England and Wales average. There were however marked variations at the local authority level (Table 1).
The highest TFR was in Blackburn with Darwen, its rate of 2.29 being well above the national average. Also in East Lancashire, the authorities with high rates were Burnley (2.09), Pendle (2.21) and Hyndburn (2.26). Chorley, Rossendale and Blackpool also recorded rates above the replacement level fertility figure. The TFR rates for Blackburn with Darwen, Hyndburn and Pendle were the 5th and 8th and 15th highest out of 326 local authorities covering the whole of England. Conversely, the TFR in Ribble Valley of 1.63 was the lowest level recorded in the broader Lancashire area in 2011 and was the 312th lowest in the country. The City of London (1.01) and Cambridge (1.37) had the lowest TFT rates, whilst Barking and Dagenham (2.45) was the only area with a rate in excess of 2.35.
Table 1 Total Fertility Rate (TFR), 2001 to 2011
Source Office for National Statistics: Key Population and Vital Statistics up to 2007; NHS Clinical and Health Outcomes Knowledge Base (search for "fertility" or similar) from 2008 onwards. From 2009, rates are available to two decimal places. The total fertility rate (TFR) is also known as the total period fertility rate (TPFR). It aims to provide a single measure of fertility that can be compared between different areas and different times. It is the number of children that would be born to a woman if current age-specific patterns of fertility persisted throughout her child-bearing life (11-49). It is obtained by summing the single-year age-specific rates for each year of age in the reproductive age range.
Replacement level fertility
The TFR can also be used as an estimate of the fertility growth factor in the population – that is whether the childbearing population is replacing itself from one generation to the next, other things being equal. In the UK and most other developed countries a TFR or completed family size of about 2.1 children per woman is required to maintain long-term population levels to take account of infant mortality and the unbalanced sex ratio at birth.
It is important to note that the level of 2.1 children is an average across all women. To ensure replacement fertility, a substantial proportion of women need to have three or more children in order to compensate for those who remain childless or have only one child. Although migration can be a significant driver of population change, for the purposes of calculating replacement fertility migration is normally ignored in Lancashire.
A total of seven of the 14 Lancashire local authorities had 2011 rates that were above the replacement the fertility rate. For England and Wales as a whole, the fertility rate has now been below replacement level since 1973.
Below replacement fertility can have demographic and socio-economic implications but these consequences are only likely to arise with persistent long-term replacement fertility. In the case of Lancashire, net inward migration and increasing levels of life expectancy both help to underpin the overall growth in population in the area.