Earliest civilizations using a barter system which gave way to importing and exporting of goods

Mesopotamia tribes were likely the starting point of the bartering system back in 6000 BC. Phoenicians saw the process, and they adopted it in their society.

Explanation:

an unexpected salary cut

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.