I wondered if it was related to breastfeeding, since it is known to have a positive correlation. It turns out breastfeeding in Norway followed the exact opposit

I wondered if it was related to breastfeeding, since it is known to have a positive correlation. It turns out breastfeeding in Norway followed the exact opposite trend: falling from the end of WWI to 1970, and picking up since then ( source: https://www.semanticscholar.org/paper/Donor-milk-banking-and-breastfeeding-in-Norway.-Grøvslien-Grønn/b7e9fe381364dcd8d118cfb5f7988ca60a56f7b8 https://www.semanticscholar.org/paper/Donor-milk-banking-and... )