Second demographic transition

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The second demographic transition (SDT) is a postulated and empirically observed decline in fertility to sub-replacement fertility as observed in developed countries, mainly European countries and Japan.

Observed features from a purely demographic perspective


  1. Substantial decline in period fertility, partly resulting from postponement of births, so that (estimated) cohort fertility of currently

reproducing women is expected to reach a maximum value well below replacement.

  1. Substantial decline in the total first marriage rate associated with an increase in mean age at first marriage
  2. Strong increase in divorce (where allowed) and in the dissolution of unions
  3. Strong increase in cohabitation, even in countries where this was not a traditional practice
  4. Strong increase in the proportion of extra-marital births
  5. Catalytic shift in contraceptive behaviour with modern means replacing traditional methods.

Observed sequence of events

  1. Decline in total fertility rate due to a reduction in fertility at higher ages, decline in crude birth rate at higher birth orders
  2. Avoidance of premarital pregnancies and "forced" marriages (such as shotgun marriages)
  3. Notwithstanding that, the mean age at first marriage continues to decline for a while (???)
  4. Postponement of childbearing within marriage, fertility of young women declines, lower order birth rates decline, this accentuates decline in period TFR
  5. Increase in judicial separation and divorce (when allowed)
  6. Postponement of marriage largely replaced by pre-marital cohabitation, increase in age at first marriage
  7. Cohabitation becomes more popular, marriage postponed until bride is pregnant, increase in pre-marital births, increase in mean age at first birth
  8. Legislation permitting sterilization and abortion further reduces unwanted fertility: fertility at border ages of childbearing declines further
  9. Cohabitation gains further support, and is frequently also preferred by the widowed and the divorced
  10. Cohabitation increasingly seen as an alternative to marriage, extra-marital fertility increases
  11. TFR's tend to stabilize at low levels
  12. TFR's increase slightly where women who postponed births start their fertility careers; increase of lower order birth rates at higher ages of childbearing
  13. Not all postponed births can be born in years of childbearing remaining
  14. Voluntary childlessness becomes increasingly significant
  15. Completed cohort fertility appears to stabilize at sub-replacement fertility levels.