These things are true, but it wasn't long-distance trade or scientific progress which made English people richer in 1400 than in 1350. It was more land per peas

These things are true, but it wasn't long-distance trade or scientific progress which made English people richer in 1400 than in 1350. It was more land per peasant. That things did not completely fall apart when the plague hit may be due to having relatively strong institutions, but again I'd argue that what mattered here was at the parish level, not Rome. Ethiopia was also quite a centralised state in medieval times (with a uniting church language playing a role like Latin's). But we don't actually know whether it suffered a larger or smaller plague at that time, it seems. We do know that it did not suffer collapse on the scale of pre-Colombian American civilisations, that we would certainly know about already.