That helps. I think you misunderstood - what I was trying to say was something quite similar: the person I replied to (who I think wasn’t you) was talking about access to family planning, and I was saying this has been available in developed countries for a long time. So although it did lead to a decrease in birth rate decades ago, it’s only recently that we see sub-replacement rates, so that latter effect specifically is likely not to do with access to family planning.

Hope that also helps, haha!