[SMARTY]

“...However, with a finite supply of silver and gold entering the empire, Roman spending was limited by the amount of denarii that could be minted...”

Reading Edward Gibbon's “Decline and Fall of the Roman Empire”, he is clear about what happened to the economy.

To paraphrase, he said that there was not enough gold and silver (etc.) for the valuation of commodities. So, slaves became currency.

A person's wealth could be calculated based on the number of slaves he held.

[FarCenter]

A similar phenomena occurred in Great Britain and the US causing the “Long Depression” from 1873 to 1896.

The rapid expansion of their economies was not supported by increased supply of gold, exacerbated by the US going on the gold standard and demonetizing silver.

It was alleviated after the discovery of gold in South Africa in 1886 and the later Yukon gold finds.