Well the key is fighting underconsumption. Automation is a somewhat negative feedback loop in that excess labor reduces the demand for further automation. This

Well the key is fighting underconsumption. Automation is a somewhat negative feedback loop in that excess labor reduces the demand for further automation. This is why anything shirt of general A.I.—which economically is automation that spills over from jobs one tries to automate to a significant portion of others—is not revolutionary. So a declining working age population could shrink the economy, and this would be the orthodox economist position which doesn't recognize a structural underconsumption problem. And with underconsumption I think it's a not of a toss-up, but if the underconsumption is prevented, I don't the the demographics will get in the way. tl;dr lock in your UBI before the population peaks.