...silver content was only equal to 1.5 denarii. This helped create inflation - people rapidly hoarded the denarii, while both buyers and sellers recognised the new coin had a lower intrinsic value and elevated their prices to compensate. Silver bullion supplies were running short since the Roman Empire was no longer conquering new territory, and because a series of soldier emperors and rebels needed coin to pay their troops to buy loyalty. So each new issue of the antoninianus had less silver in it than the last, and each contributed to inflation. By the late third century the coins were almost entirely made of bronze from melted down old coins like the sestertius. Vast quantities were being produced, with a large proportion of the stocks being contemporary forgeries, often with blundered legends and designs. Individual coins were by then practically worthless and were lost or discarded by the millions.Ben Bernanke must have skipped class the day they covered this.
* While everybody knows the names "Caligula" and "Nero", the former is probably unfairly maligned and the latter wasn't a half-bad emperor until he slipped Seneca's leash. Caracalla, on the other hand, was a piece of work from the jump off and an unmitigated disaster as emperor.