Results can start to be worthwhile early on. But the life-altering decisions people make over a two year period when guaranteed a subsidy that runs out at the end of those two years are not particularly likely to be the same as the life altering decisions people make over a two year period when guaranteed that subsidy for life.
(If you wanted to really understand all the dynamics, you'd probably want to wait more than a generation to understand how subsidy recipients' decisions to raise children are affected and whether those children make systematically different life choices.)
(If you wanted to really understand all the dynamics, you'd probably want to wait more than a generation to understand how subsidy recipients' decisions to raise children are affected and whether those children make systematically different life choices.)