Taxes, trade and crafts
The economic development of Germania Inferior and Gallia Belgica was not identical. The Rhine zone was a slow starter. It was almost a century after the foundation of Belgian cities like Cassel, Thérouanne, Bavay and Tongeren, that the Rhine towns Voorburg, Nijmegen and Xanten started to grow. This was not the only difference. As we have already seen above, Germania Inferior was a 'tax importing zone' and Gallia Belgica was a 'tax exporting zone'.
The Roman government had to pay the soldiers of the Rhine army, but received almost no taxes from Germania Inferior, which was not densely populated. To pay for 20,000 soldiers, 250,000 tax paying families were necessary, and there were simply not so many people in the Rhine towns. Therefore, Germania Inferior received more from Rome than it had to pay. It benefited economically from the occupation.
So much money was invested in this province, that the towns became too big. E.g., second-century Nijmegen had some 5,000 inhabitants, more than the Batavian economy could feed. Many people from Nijmegen were entrepreneurs selling products and services to the soldiers. The town must have been a rich entertainment center, but was completely dependent upon the army and therefore economically vulnerable. Without army, there was no money; and without money, there was no food. In spite of the investments, the economy of the Dutch river area remained unbalanced - and fatally so, as we will see below.
From a financial point of view, Gallia Belgica suffered from the Roman occupation. The central government did not invest in this region but demanded taxes. And yet, Belgica was lucky, because it was a development zone. As we have seen above, the area became part of a market economy and started to produce salt, iron, cattle, ham, and terra nigra ceramics. Wheat and barlkey were sold to the Rhine army.
Other economic activities are mentioned by the Roman author Pliny the Elder, who visited Belgica in 75. He explicitly mentions geese, which were brought to Rome (to be consumed) and offered white feathers. Soap was another product, which was used by Italian women to bleach or paint their hair.
One of the articles made in Germania Inferior was perfume from Cologne. One of its inhabitants, a man named Sextus Haparonius Justinus, is known to have been a perfume salesman. It is tempting to see in his activities a predecessor of the modern Kölnisches Wasser, especially since many perfume phials have been found.
The Low Countries also exported articles made of tin and iron, skins, cattle, and woman's hair. (When the last-mentioned product was blonde, it was used to make wigs. Otherwise, it was used in catapults.) Germania Inferior also played a role in the trade of amber, horses, Germanic slaves, and British silver. But the most important article remained corn, which was sold to the Roman army.
Industry also benefited from the tax incentive. Native artisans became acquainted with new tools. For example, the carpenter discovered the claw hammer, the square, several new types of saw, and the plane. The plane-tree produced fine wood. Other craftsmen started to use the plumb line and surveyor's pole. The potter's wheel was another innovation. Morini and Menapians were famous for their salt, and the Nervians were well-known as producers of cloth. (This industry was to become famous in the Middle Ages.)
Zinc had already been produced before the arrival of the Romans (near Stolberg in the Eifel), but the newcomers introduced new techniques. There were several stone quarries: the produce of the quarry near Tournai (in Gallia Belgica) was used throughout the valley of the Scheldt. Because land transport was expensive, the rest of Germania Inferior used tuff from the valley of the Moselle and limestone from Loraine, which could be brought downstream along the Rhine. Finally, marl was quarried near Valkenburg (in Dutch Limburg). Pliny the Elder tells that it was used to make roof tiles, but we still lack archaeological confirmation of his statement.