A Study on the Short- term Fertility Projection …...A Study on the Short- term Fertility...
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A Study on the Short- term Fertility Projection Method Using Marriage Rates - Population Projections for the Republic of Korea Belgrade, 25 Nov 2019
Transcript of A Study on the Short- term Fertility Projection …...A Study on the Short- term Fertility...
A Study on the Short- term Fertility Projection Method Using Marriage Rates
- Population Projections for the Republic of Korea
Belgrade, 25 Nov 2019
- Contents -
1
Population Projections for Korea2
Marriage and Fertility Indicators 3
2019 Fertility Projection Method4
Fertility trends in Korea
1. Fertility trends in S. KOREA
Figure 1.Changes in Fertility Indicators in KOREA, 1970~2018
2. Population Projections for KOREA
Figure 2. Cohort Component Method
Population by sex and age, t-1 year
Age specific fertility rate
Sex ratio at birth
Births by sex
Population of aged 0
Population by sex and age, t year
Survival ratioby sex and age
International net migrationby sex and age
Population of aged 1 - 100+
Total Fertility Rate 2015 2016 2017 2018 2019 2020
2016
Projections
Medium-growth 1.24 1.18 1.20 1.22 1.23 1.24
Low-growth 1.24 1.16 1.14 1.13 1.11 1.10
Actual Observation 1.24 1.17 1.05 0.98 - -
Figure 3. Observed and Projected Total Fertility Rate
2. Population Projections for KOREA
- Actual observed value was lower than the low growth scenario in 2016 projections
3. 2019 Fertility Projection Method
Time Series Model
Generalized Log Gamma Distribution Model
- f(x): Fertility rate at age x
- C: A birth cohort’s fertility rate
- u, b:Mean age at childbearing and standard deviation of mean age at childbearing
- λ: Distribution (constant)
Figure 4. long-term fertility projection model
In Korea, around 98 percent of children are born in wedlock
Figure 5. Births by Marital Status
3. Marriage and Fertility Indicators
2000 2005 2010 2015 2016 2017 2018
0.75 0.72 0.78 0.80 0.75 0.70 0.68
Figure 6. Cumulative Marriage Rates for Women Under 40, 2000-2018
(unit: number of events per woman)
Figure 7. Age Specific Marriage Rates Figure 8. Cumulative Marriage Rates
3. Marriage and Fertility Indicators
Figure 9. Childbirth-to-marriage Ratio, 2009-2018
2011 2012 2013 2014 2015 2016 2017 2018
total 1.62 1.66 1.50 1.53 1.57 1.51 1.39 1.33
1 birth 0.83 0.86 0.78 0.81 0.85 0.84 0.79 0.78
2 births 0.61 0.63 0.57 0.57 0.58 0.54 0.48 0.45
3 or more 0.18 0.17 0.16 0.15 0.14 0.14 0.12 0.10
(unit: number of live births per marriage, cumulative of women under 40)
3. Marriage and Fertility Indicators
Figure 10. Average Age at Marriage and Fertility
3. Marriage and Fertility Indicators
Short-term Fertility Projection Method
𝑇𝐹𝑅𝑡: Total fertility rate at time t
𝑀𝑠,𝑡: Marriage-period-weighted average cumulative marriage rate for birth order
𝑏𝑠,𝑡: Birth rate by birth order s(1, 2, 3+) at time t per married woman
𝑚𝑘: Cumulative marriage rate until 39 during time k of marriage period
𝑤𝑠,𝑘: Weight of percentage of birth at time k of marriage period by birth order
𝑘 : Marriage period
𝑝𝑠,𝑘: Percentage at time k of marriage period by birth order
𝑇𝐹𝑅𝑡 =
𝑠
𝑀𝑠,𝑡 𝑏𝑠,𝑡 + 𝑒𝑡
𝑀𝑠,𝑡 =
𝑘
𝑚𝑘 𝑤𝑠,𝑘
𝑤𝑠,𝑘 =𝑝𝑠,𝑘 𝑘 𝑝𝑠,𝑘
4. 2019 Fertility Projection Method
𝑌𝑥= ln − ln𝑀𝑥𝑀𝑥: Cumulative marriage rate until 𝑥
𝑌𝑥,𝑡=𝑎𝑥 + 𝑏𝑥𝑘𝑡 + 𝜀 𝑥,𝑡Gompit Model Lee-Carter Model
Calculating the cumulative marriage rates by year: M
𝑀𝑠,𝑡 =
𝑘
𝑚𝑘 𝑤𝑠,𝑘
𝑚𝑘: Cumulative marriage rate until 39 during time k of marriage period
𝑤𝑠,𝑘: Weight of percentage of birth at time k of marriage period by birth order
𝑘 : Marriage period
1
Calculating the time-weighted average of cumulative marriage rates
birthorder t-0 t-1 t-2 t-3 t-4 t-5 t-6 t-7 t-8 t-9
1 birth 0.382 0.322 0.139
2 birth 0.194 0.229 0.178 0.119 0.075
3 or more 0.101 0.131 0.129 0.113 0.094 0.076
𝑤𝑠,𝑘 =𝑝𝑠,𝑘 𝑘 𝑝𝑠,𝑘
𝑝𝑠,𝑘: Percentage at time k of marriage period by birth order
𝑤𝑠,𝑘: Weight of percentage of birth at time k of marriage period by birth order
2
Calculating the fertility-to-marriage ratio by birth order is projected
by using the L-C model.
Medianvalue 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022
total 1.62 1.66 1.50 1.53 1.57 1.51 1.39 1.33 1.31 1.29 1.27 1.26
1 birth 0.83 0.86 0.78 0.81 0.85 0.84 0.79 0.78 0.78 0.78 0.77 0.77
2 births 0.61 0.63 0.57 0.57 0.58 0.54 0.48 0.45 0.44 0.42 0.41 0.40
3 or more 0.18 0.17 0.16 0.15 0.14 0.14 0.12 0.10 0.09 0.09 0.09 0.08
Figure 10. Childbirth-to-marriage Ratio, 2009-2022
(unit: number of live births per marriage, cumulative of women under 40)
3
𝑇𝐹𝑅𝑡 =
𝑠
𝑀𝑠,𝑡 𝑏𝑠,𝑡 + 𝑒𝑡
𝑇𝐹𝑅𝑡: Total fertility rate at time t
𝑀𝑠,𝑡: Marriage-period-weighted average cumulative marriage rate for birth order
𝑏𝑠,𝑡: Birth rate by birth order s(1, 2, 3+) at time t per married woman
The total fertility rates by year are calculated as the sum of the
timed-weighted averages of cumulative marriage rates by birth order
multiplied by the fertility-to-marriage ratios.
4
5. Results of the 2019 Fertility Projection
Figure 11. Total Fertility Rates by Scenario, 2017~2067
TFR 2017 2018 2019 2020 2021 2025 2030 2040 2050 2067
Mid 1.05 0.98 0.94 0.90 0.86 1.00 1.14 1.27 1.27 1.27
# of births(thousand) 348 325 309 292 290 335 358 295 240 212
High 1.05 0.98 1.03 1.06 1.09 1.23 1.38 1.45 1.45 1.45
Low 1.05 0.98 0.87 0.81 0.78 0.84 0.97 1.09 1.10 1.10
5. Results of the 2019 Fertility Projection
Figure 12. Differences between 2016 and 2019 Results – TFR
1.2
1.38
1.05
0.98
0.86
1.27
0.8
0.9
1
1.1
1.2
1.3
1.4
2017 2020 2023 2026 2029 2032 2035 2042 2045 2048 2051 2054 2057 2060 2063
2016 2019
5. Results of the 2019 Fertility Projection
Figure 13. Differences between 2016 and 2019 Results – Number of Live Births
YearNumber of live Births (unit: thousand persons)
2016 (A) 2019 (B) (A-B)
2017 413 348 -65
2018 411 325 -86
2019 410 309 -101
2020 409 292 -117
2021 410 290 -120
2022 411 300 -111
2023 413 312 -101
2024 415 324 -91
2025 417 335 -82
2026 418 346 -72
2027 417 356 -61
2028 415 361 -54
2029 412 360 -52
2030 406 358 -48
