Here is an ugly truth some investors dont seem to realize, in one hand they say "its ridiculous to own the 10y treasury at 0.6% or the 30y treasury at 1%" on the other hand they say "stocks are cheap relative to interest rates". Both of these things dont go together because if you are long stocks due their 'cheapness to interest rates' you are also long bonds!
In the sense that if bonds were to collapse and rates rise (The fed does not control long-term interest rates), stocks would not longer be cheap vs interest rates and therefore stocks would collapse with them!
This is the reason why I'm skeptical of being long US stocks in a period of rising deficits, rising deficit monetization, record liquidity injections and future entitlement problems.
Stock investors are now bond investors, whether they are aware of it or not!
Sort of. I think the long stock thesis has a few other elements:
1) At the index level (not so much at the individual issue level) stocks are effectively a risk-free asset. Assuming that the next 30 years in the USA will be like the last 30 years in Japan, with no inflationary breakout, no sovereign debt crisis etc., long term allocators should be rationally willing to drive the ERP far below historical average levels - maybe to 1% or less.
2) The psychological effects of ZIRP/NIRP are enormous. Psychologically, the difference between earning 2.5% and 0.5% on your fixed income is (I'd argue) far greater than a 4.5% vs. 2.5% differential. As you approach the zero bound investors become desperate to obtain any scrap of positive yield which leads to irrational behavior, like bidding up large cap indices to PEs of 40, 50 or beyond.
3) Speculative mania is always a possibility in the stock market and could drive stocks to truly insane levels (like the Nasdaq at 100x PE).
In other words I'm coming from the opposite direction as you are: if long bonds pays off then being long stocks will almost certainly pay off much more, whereas if stocks tank then a bond portfolio is likely bleeding too.
In either case, the most important thing is IMO to look for signs that an inflationary breakout is actually under way, and panic at that time. Alternatively, stocks could get bid up to where there clearly isn't any premium left to be captured (which I think is what will happen over the next 3-5 years). At that point, the days of actually earning something from a passive portfolio will be over, at least for investors holding USD assets.
Why? This did not happen in Japan even though they had and are expected to have ZIRP until the end of time. Japan stocks are actually cheaper now than they are in the US, even though they were in ZIRP for much longer