It's not only developing countries that benefit from increased female participation in the labour force. For Western nations, the increased proportion of women

It's not only developing countries that benefit from increased female participation in the labour force. For Western nations, the increased proportion of women in the labour force was a core component of the rapid increased economic growth between the 1940's and today. Low fertility is an interesting thing where it comes to development; for most countries it has quite dramatically declined as incomes have increased. The effects are likely bidirectional (increased economic growth -> lower fertility rate; lower fertility rate -> increased per capita income). The drivers are complex and interrelated: high child mortality rates, low life expectancy, and high poverty are associated with high fertility. It's an unjust comparison to make, however leading theories share common features with K-r reproduction strategies in ecology (with increased survival / longevity, investing in a few highly educated/skilled children becomes feasible). Similarly, increased education / maternal health is highly correlated with economic development and child wellbeing. These are often highly compounding effects over time - a virtuous cycle in which increased economic freedoms, health, education, and opportunities (male and female - often females are relatively impoverished, so there's the potential for bigger immediate benefits) can lead to rapid development with the right institutional conditions.