It is widely assumed that the most important factor leading to large family sizes and fast population growth is the lack of availability of contraception.

But Tim Worstall's book Chasing Rainbows says:

...the availability of contraception only explains 10% of the changes in total fertility

The data behind this is sourced from an old world bank report (pdf).

Does modern contraception only account for 10% of the reduction in fertility we observe in actual populations?

  • How would one even begin to quantify this? – gerrit Feb 23 '15 at 22:18
  • @gerrit statistical comparisons over time and across countries. – matt_black Feb 23 '15 at 22:21
  • 3
    It does make sense: the availability of modern contraception is not enough. People must know how to use it, and be motivated how to use it. It is a necessary but not a sufficient requirement. And probably not a limiting factor in practice. Statistically, factors such as female literacy, and cultural factors, are likely way more important. Problem is that those other factors might correlate (in time and area) with contraceptive availability. I don't currently have any sources for this, hence I post as a comment rather than an answer. – gerrit Feb 23 '15 at 22:25
  • now is this 10% in the world, or is this 10% for any given country? looking at europe would probably give you the best statistics, because their population is stagnant/receding so this would lead me to the conclusion they use birth control effectively plus general consensus not to have children. or if birth control isnt used then abortions must make up for the unplanned pregnancies. in essence its hard to not have 0-1 child unless birth control is used. – Himarm Feb 23 '15 at 23:41
  • @Himarm It's 10% of the cause of any change in fertility over time (I presume). Perhaps major changes to fertility precede the wide availability of contraception in countries seeing large fertility reductions. Perhaps we are perfectly capable of avoiding unwanted reproduction when we have the willpower and contraception just makes that easier. – matt_black Feb 23 '15 at 23:47

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