Because the monetary regimes of, say, the late 20s, or the early 50s, or even into the late 70s and into the deregulatory periods of the 1980s are so vastly dif

Because the monetary regimes of, say, the late 20s, or the early 50s, or even into the late 70s and into the deregulatory periods of the 1980s are so vastly different than what exists now, that a comparison across vast timeframes would be completely specious. Not sure that is explicitly what they were trying to accomplish, but that is what I got out of the graphic.