, ,

An attempt to control the rates for call loans by the establishment
of an arbitrary limit at a low level, without the
ability to modify the causes above enumerated, which operate
to increase rates, would be distinctly hazardous, for
the reason that up to the point where the arbitrary rate
would limit the supply of new money, speculation and expansion
might proceed unchecked and the natural elements
of correction or regulation would not obtain. In
other words, high rates act as a deterrent to over-speculation
and undue expansion of credit. On the other hand,
should the supply of money available at a fixed maximum
rate become exhausted, liquidation might suddenly be
forced, because the demands for additional accommodation
for the consummation of commitments already made could
not be met. The effect of such liquidation would be to
embarrass not only investors and dealers in securities, but
frequently might affect dealers and merchants in commodities
as well.

Federal Reserve Bulletin, April, 1920

“Over-speculation and undue expansion of credit” is the only thing holding up the present-day stock bubble in the United States. Graph below:
Since 1991, there has been less and less average stock market wealth per average dollar of margin debt on the New York Stock Exchange.