Increased trade is a major source of improved economic activity and income. This point was demonstrated by classical economists, then extended to international trade. While the theories have been refined, the principle remains unchallenged. Open countries benefit most from the expansion of international trade. Countries with low trade volumes have experienced mediocre rates of improvement in their economic conditions.

It can also be seen that during the long period of post-war growth for industrialised countries, which was then extended to globalisation, international trade progressed faster than growth, even if, in the recent period, this has been seen mainly in emerging countries.

In a recent article in Foreign Policy, Bret Devereaux looks back at the long period of the Roman Empire, focusing primarily on the dimension of trade within the Mediterranean.
He notes an intensification of trade, the establishment of trading posts and at the same time a strong improvement in the well-being of the regions participating in this dynamic. One measure of the intensification of trade is the number of merchant ships that were shipwrecked. From 20 to 40 per half-century between 500 and 200 BC, this number increases to 100 between 150 BC and 100 AD. In addition, the ships become much larger and the journeys are no longer those of coastal shipping but take back roads on the Mediterranean. Finally, Roman currency facilitated trade, creating the conditions for its acceleration.
The dynamics of trade also allows for better regional planning and maritime security.
Trade and growth also brought greater revenue to the Roman Empire.
The equation is virtuous.

And then, the civil wars within the Empire caused a form of fragmentation of the territory with an additional desire to centralize decisions whereas until then the rules had been very decentralized, particularly regarding price fixing.
This change in the organization of space and the rules governing trade gradually caused a decline in trade, contributing to the end of the Roman Empire. The beautiful construction died out, and this civilization, which enlightened the world and still astonishes us, disappeared.

We should not draw a parallel with the current situation and the rule changes that are shaking up all the players in the globalized economy under American impetus. But we must be careful that the current gesticulations do not result in a fragmentation of the world. The resulting multipolar world, with different currencies, would multiply situations of heterogeneity and dysfunction, to our own peril.