I'd venture to guess that the choices you mention did not always carry the sort of consequences they do today.

You're right, policy decisions don't cause more people to have kids at a young age. They do however, have an effect on joblessness [1], just to name one facet of the economic environment that now exists in the US.

[1] http://www.google.com/publicdata/explore?ds=z1ebjpgk2654c1_&...