Explanations for fluctuations in fertility
Fertility follows some long-term trends, but there are also minor year-to-year fluctuations. This page explains the possible sources of fluctuations.
There are some obvious culprits:
- Definitional ambiguity
- Random variation
- Measurement error
We discuss factors that cannot be reduced to these ones.
Superstitions associated with specific years
This phenomenon operates particularly in East and South-East Asia: some years are considered very lucky for having babies, whereas some years are considered very unlucky for having babies.
Examples:
| Year | Country | Fertility information | Considered auspicious or inauspicious? | TFR two years before | TFR one year before | TFR that year | TFR next year | TFR two years later | TFR source |
|---|---|---|---|---|---|---|---|---|---|
| 1966 | Japan | fertility in Japan | inauspicious | 2.045 | 2.145 | 1.579 | 2.224 | 2.127 | Human Fertility Database for all years |
| 1988 | Singapore | fertility in Singapore | auspicious (Dragon Year) | 1.43 | 1.62 | 1.96 | 1.75 | 1.83 | UN data compiled by Gapminder for all years |
| 2000 | Singapore | fertility in Singapore | auspicious (Dragon Year) | 1.48 | 1.47 | 1.6 | 1.41 | 1.37 | UN data compiled by Gapminder for all years |
| 2010 | Taiwan | fertility in Taiwan | inauspicious | 1.05 1.05 |
1.022 1.03 |
0.887 0.895 |
N/A 1.065 |
N/A 1.265 |
First row is Human Fertility Database data, second row is UN data compiled by Gapminder. HFD data goes only till 2010. |
| 2012 | Singapore | fertility in Singapore | auspicious (Dragon Year) | 1.267 | 1.275 | N/A | UN data compiled by Gapminder for all years | ||
| 2012 | Taiwan | fertility in Taiwan | auspicious | 0.895 | 1.065 | 1.265 | N/A | N/A | UN data compiled by Gapminder for all years |