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Fertility Assumptions

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The following chapter contains the fertility assumptions agreed by the Expert Group and the issues considered in reaching their decision.  Based on their analysis the Expert Group considered that the most likely out-turn for overall average fertility over the projection period, as measured by the Total Fertility Rate (TFR), would be in the range 1.8 to 1.6.  

Two variants were chosen: a high variant (F1) which assumes that TFR will remain at the 2016 level of 1.8 for the lifetime of the projections and a low variant (F2) which assumes that TFR will decrease to 1.6 by 2031 and remain constant thereafter.

Fertility Assumptions Agreed

F1: Total fertility rate to remain at the 2016 level of 1.8 for the lifetime of the projections
F2: Total fertility rate to decrease from 1.8 to 1.6 by 2031 and to remain constant thereafter to 2051

The main items deliberated on prior to reaching agreement are discussed in the subsequent sections, including:

- Historical and recent trends in births
- Age specific fertility rates
- Number of women of child bearing age
- Average age of first time mothers
- Comparisons with other European countries

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The number of births each year in Ireland has varied over the past 50 or so years, rising from just under 60,000 in 1961 to a peak of over 74,000 in 1980.  This was followed by another period of decline, with just 48,250 being recorded in 1994. The number of births peaked again in 2009 reaching 75,550.  Births have declined steadily since 2009, with fewer than 65,000 births recorded in 2016.

Thousands
196060.7
196159.8
196261.8
196363.2
196464.1
196563.5
196662.2
196761.3
196861
196962.9
197064.4
197167.6
197268.5
197368.7
197468.9
197567.2
197667.7
197768.9
197870.3
197972.5
198074.1
198172.2
198270.8
198367.1
198464.1
198562.4
198661.6
198758.4
198854.6
198952
199053
199152.7
199251.1
199349.3
199448.3
199548.8
199650.7
199752.8
199854
199953.9
200054.8
200157.9
200260.5
200361.5
200462
200561.4
200665.4
200771.4
200875.2
200975.6
201075.174
201174.033
201271.674
201368.954
201467.295
201565.909
201663.897
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The main factors which impact on the number of births are the number of women of child bearing age (15 - 49 years) and their fertility levels. The total fertility rate (TFR) was as high as 4.03 in 1965 but it has fallen steadily thereafter. The age specific fertility rates (ASFR) also show a general decline with a rate of 228.7 for women aged 25 - 29 in 1970 down to 75.1 in 2016. Similar trends can be observed in all age groups, with those aged 30 - 34 falling from 201.9 to 122.5 in 2016 while the 20 - 24 age group fell to 38.6 (from 145.5 in 1970). See table 4.1.

One exception to the secular decline is when the fertility rate rose from 1.85 in 1995 to 2.1 in 2008. This may have been caused by the tempo effect, which is the effect of women in their twenties delaying having children until their thirties or early forties. This causes a temporary decline in the fertility rates and then a recovery as the delayed births occur.  Indeed the ASFR for those aged 30 - 34 rose from 123.5 in 1995 to 140.1 in 2008, while the fertility rate for those aged 35 - 39 years rose from 60.3 to 100.6 in the same year.  However the rates subsequently resumed their downward trend.

Show Table: Table 4.1 Age specific and total fertility rates, 1960 - 2016

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Not only are the age specific fertility levels declining, but the number of women in the younger age groups is also falling.  For example, the number of women aged 20 - 29 has been in decline in recent years, falling from 383,000 in 2009 to nearly 287,000 in 2016 (-25.1%), while the number of women aged 30 - 39 has remained static at around 385,000 since 2012.  This can be compared to the period between 1991 and 2008 when the number of women aged 20 - 29 grew by almost 135,000 (52.7%) and the number of women aged 30 - 39 increased by 108,500 (44.3%).  The combination of declining fertility rates allied with a decrease in the number of women of child bearing age has resulted in the fertility rate falling from 2.10 in 2010 to 1.82 in 2016 or a decline of 13.3%.  See table 4.2 and fig 4.2.

Show Table: Table 4.2 Number of females for selected age groups and years

20-2435-39
197123.414.4
19722413.8
197324.312.9
197424.212.7
197524.311.9
197623.911.5
197723.511.4
197822.811.7
197922.611.2
198022.511.9
198122.112.3
198221.412.8
198321.312.9
19842113.1
198519.813.3
198619.213.5
198718.313.4
198817.513.5
198916.314
199015.514.1
199115.814.3
199215.514.6
199315.114.6
199414.815.1
199514.715.6
199614.916.3
199714.116.7
199814.317.4
199914.217.6
200014.518.5
200114.518.7
200214.219.4
200313.719.8
200413.320.6
200512.721.7
200612.822
200712.522.2
200812.422.5
200911.723
201010.823.3
20119.923.9
20129.624.9
20139.325.9
20148.827
20158.728.1
20168.229.4
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The Expert Group also noted that the age at which women are deciding to have their first child is rising year on year and that this would impact on future fertility rates if the trend were to continue. There has been an increasing trend towards later births, with the average age of first-time mothers rising by 7.5 years for those inside marriage between 1975 and 2015 and by 6.3 years for those outside marriage over the same period (21.8 to 28.1 years).  See fig 4.3.

 

Within marriageOutside of marriage
197525.321.8
197625.421.7
197725.621.8
197825.621.6
197925.621.5
198025.621.5
198125.721.4
19822621.4
198326.221.4
198426.521.6
198527.221.8
198627.422
198727.721.9
19882822.1
198928.121.9
199028.321.9
199128.421.9
199228.722.1
199329.122.3
199429.422.4
199529.722.7
199629.922.9
199730.123.1
199830.323.2
199930.623.3
200030.623.6
200130.723.9
200230.724.2
20033124.6
200431.224.9
200531.425.1
200631.425.3
200731.325.6
200831.325.8
200931.426.2
201031.626.6
20113227
201232.127.3
201332.427.7
201432.728
201532.828.1
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The high fertility assumption F1 assumes the total fertility rate will remain at the level observed in 2016 of 1.8 for the lifetime of the projections up to 2051.  This assumption sees fertility levels remaining below the theoretical replacement level (2.1) but still close to the top of the EU fertility table.  See Fig 4.4.

The low fertility assumption F2 assumes the total fertility rate will decrease from 1.8 to 1.6 by 2031 and then stabilise at this level until the end of the projection period in 2051. The Group considered that this assumption would allow Ireland to remain in line with the 2016 EU average fertility rate while still allowing a decrease to take place from the current level.

X-axis labelFertility rate
France1.92
Sweden1.85
Ireland1.81
Denmark1.79
United Kingdom1.79
Latvia1.74
Iceland1.74
Norway1.71
Lithuania1.69
Belgium1.68
Netherlands1.66
Romania1.64
Czech Republic1.63
Germany1.6
Estonia1.6
Slovenia1.58
Finland1.57
Albania1.56
Bulgaria1.54
Switzerland1.54
Hungary1.53
Austria1.53
Slovakia1.48
Croatia1.42
Luxembourg1.41
Poland1.39
Greece1.38
Cyprus1.37
Malta1.37
Portugal1.36
Spain1.34
Italy1.34
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It is assumed that the rate of decline in fertility under F2 will be uniform across all age groups. While there has been some variation in the way the fertility of women in different age groups has evolved in recent years, adjusting age specific rates within the agreed overall TFR has little impact on the total number of births. Furthermore, given that the principal purpose of the fertility assumptions are to generate projected annual number of births to feed the projection model, the distribution of these births according to the age of the mothers is considered to be of secondary importance. The assumed age-specific and derived total fertility rates under assumption F2 are given in Table 4.3.

Show Table: Table 4.3 Actual 2016 and assumed age specific and total fertility rates under fertility assumption F2

While this report contains a number of summary tables, detailed results of the population projections from 2017 to 2051 are available on the CSO Statbank here.

Go to: Mortality Assumptions