Basically all countries that started having some economic growth since 1950 will have this spike effect. The countries that were already rich had a slow population transition, the other ones a fast one. The short version of that story is that in the latter child mortality went down slowly, and in the the former it was a quick proces. People take some time to adapt to this new reality, which means that for a shirt period of time 10 of 10 children will grow up to have kids of their own. After a while, the amount of children goes down to 2 or less, and growth stops. In Europe, this lade population multiply by two or three, in North Africa for example it can be up to times five or more. And in modern societies, this kind of growth tends to concentrate in cities.

Just having the vote on a non working day or giving (almost) everyone obligatory paid leave that day is way easier and could already have quite an impact.