Ben Wilson at LSE has posted a very nice blog in Demotrends about the relationship between demography and democracy, building on his work with Tim Dyson. Their analysis is that the kinds of societal changes associated with the demographic transition are those that also tend to promote democracy in societies:
In the second half of the demographic transition, the proportion of adults in the population becomes larger. In demographic terms, fewer children means that the number of people eligible to vote increases, as does overall civic engagement. Put bluntly, children aren’t interested or engaged in politics.
Another consequence of demographic transition is that when women are caring for fewer children they are more likely to enter the labour market. Women are able to pursue careers, skills, and training in a way that they aren’t able to if they are caring for large families. As a result, they tend to have a greater interest in the political system and their rights.They then show the statistical relationship between the Vanhanen Index of democracy and the median age as a proxy for where a country is in terms of the demographic transition. The relationship isn't perfect, but it is very intriguing. Now, full disclosure, I have been following Tim Dyson's work forever, and I doubt that I have ever disagreed with anything he wrote. Indeed, if you go back and look at my blog post about the Colombia peace agreement, you will see some similarities with this theme that democracy and demography are intimately related.