Another primary consideration in introduction & eventual disappearance of Segmentata?

[ValentinianVictrix]

One bit of evidence of an increase in wealth during the 4th century AD could be linked to an episode when the Emperor had to ban the sale of iron/iron ore to the Sassanids, said iron was being used to make arms and armour for the Sassanid military. It would only be possible for merchants to sell iron if there was a surplus due to increased production. Increased production increases the amount of wealth that is circulating around the Empire, through more workers being hired who then spend their pay on a variety of goods, which in turn leads to an increase in such goods having to be produced, which leads to hiring new workers which leads to.... I think you get what is happening then.