Bubbles, bubbles everywhere, waiting to burst?

The big lesson for central banks from the bursting of the sub-prime mortgage bubble was that monetary policy has to go beyond narrow focus on price stability and also address financial stability. 

It is therefore remarkable that quantitative easing continues unabated even as asset prices are frothing across markets - bonds, stocks, property, and even cryptocurrencies! In some cases like Sweden, as Zero Hedge points out, real housing prices are well past their highest levels since 1875! In fact, they are at more than double their previous high. 

And despite this, the Riksbank prefers to continue monetary accommodation by retaining rates at minus 0.50%! Of course, it does not help that its monetary policy is locked into ECB's monetary policy stance. 

The real estate markets in Canada and Australia are not far behind. And junk bond spreads in the US are threatening to touch their lowest in the past two decades. Credit spread for investment grade bonds is just a percentage point! Long-term global real interest rates are at historic lows. 

In the US, the Shiller CAPE, which compares the S&P 500's current price to the 10 year average of earnings, stands at a ratio of 31, indicating that stocks are about 50% over-valued on historic average, a figure exceeded only once in the past 60 years! 

In fact, over a longer historical sweep, the average stock is trading at 73% above its historical average, higher than all but two occasion since 1880 - just before the Great Depression and the run-up to the 1999 dotcom bubble bursting.

It is a moot point as to what is the main driver of the extraordinary low interest rates in developed countries. While on the supply-side the global savings glut, arising from shifting demographics, and on the demand-side structural changes have lowered the cost of capital investment, it cannot be denied that the QE has hastened the downward trend of real interest rates.  

While QE was understandable when the world economy was tottering in 2008, it is surely well past time to step back. But the reluctance of central banks to roll back the extraordinary monetary accommodation is yet more proof that central banks are unlikely ever to be able to take the punchbowl away when the party is on.

Isn't this a compelling enough reason why there should be dynamic macro-prudential regulations that act as automatic counter-cyclical measures to lean against the wind when such bubbles are inflating?

Update 1 (19.10.2017)
The graphic below shows why the equity and bond markets are operating at pretty much the tail-end of the spectrum in terms of valuations.

Yet, despite the froth, short-term implied volatility has never been lower for decades.