Which cosmetic retinoids survive in the bottle

Researchers at the University of Ljubljana tested sixteen retinoid derivatives found in twelve commercial cosmetic products, measuring how much of each survived over six months of normal storage, under accelerated heat conditions, and after light exposure. Hydroxypinacolone retinoate came out the most stable of the group. This is the strongest genuinely independent finding about HPR anywhere in the published literature, and it is worth understanding for what it is. It means a product containing HPR is less likely to have degraded before you finish it, which is a real advantage over less stable retinoids. It says nothing at all about whether HPR improves skin. Those are separate questions, and the second one has not been answered.