More significant still is the behaviour of long-term interest rates.
They have fallen steadily since the 1980s and remain close to historic lows.
And that underpins all sorts of other asset prices.
A widespread concern is that the Fed and its peers have grossly distorted bond markets and, by extension, the price of all assets.
Warren Buffett, the most famous disciple of Ben Graham, said this week that stocks would look cheap in three years' time if interest rates were one percentage-point higher, but not if they were three percentage points higher.
But if interest rates and bond yields were unjustifiably low, inflation would take off - and puzzlingly it hasn't.
This suggests that factors beyond the realm of monetary policy have been a bigger cause of low long-term rates.
The most important is an increase in the desire to save, as ageing populations set aside a larger share of income for retirement.
Just as the supply of saving has risen, demand for it has fallen.
Stagnant wages and the lower price of investment goods mean companies are flush with cash.
All this suggests that interest rates will stay low by historical standards.
Still the most dangerous, anti-Graham motto of investing is “this time is different”.
It would be daft to assume that asset prices must remain high come what may.
Many hazards could derail the economy and financial markets, from a debt crisis in China to an American-led trade war or an outbreak of fighting on the Korean peninsula.
And when the next recession comes, policymakers have less fiscal and monetary ammunition to fight it than they had in previous downturns.
Prudence therefore suggests caution.