At the simplest level, Hussman's arguments are
about mean reversion of earnings yields, something that even diehard bulls like Siegel admit to.
As the great Peter Bernstein (1996) once said
about mean reversion:
If you care
about mean reversion, you can wait in cash until we get «the mother of all selloffs» and then invest.
The argument
about mean reversion in profits is several years old.
Not exact matches
I'm actively looking at my debt and determining if it makes more sense to pay down mortgages (locking in a guaranteed ~ 4 % return) or investing in bonds (~ 1 % returns if held to maturity) or stocks (uncertain, but I just wrote an article
about the current PE ratio and the inevitable
reversion to the
mean and I believe we are likely headed for 10 years of low single digit returns).
I give Grantham credit for coming to this realization (something he has done before) but I wonder how his investors feel
about it after years of playing the
mean reversion waiting game.
I was recently interviewed on Better System Trader, click here for part one of the interview,
about the steps for creating a stock
mean reversion strategy.
I think your point
about using CAPE across countries as a way of allocating money across global equity markets is a good one but it does draw on the cross sectional version of
mean reversion, not the time version that many in the market are using CAPE for right now.
In my book I wrote
about there being two lenses through which we can view financial markets:
mean -
reversion (or value) and momentum.
It is a book
about why long - term investing serves you far better than short - term speculation;
about the value of diversification;
about the powerful role of investment costs;
about the perils of relying a fund's past performance and ignoring the principle of
reversion (or regression) to the
mean (RTM) in investing; and
about how financial markets work.
With charts like this, looking at relative valuation, you can expect some «
mean reversion» over time and you have to make a judgement
about what you think is an appropriate level of premium / discount, and in turn, what you think is an attractive level.
The concept of
mean reversion is something I talk
about regularly here at Daily Price Action.
I've posted here regularly
about the implications of
mean reversion in elevated profit margins (see, for example, The Temptation To Abandon Proven Models In Speculative and Fearful Markets: Why This Time Isn't Different, What Record Corporate Profit Margins Imply For Future Profitability and The Stock Market, Warren Buffett, Jeremy Grantham, and John Hussman on Profit, GDP and Competition).
Thinking
about price momentum and
mean -
reversion are also lesser matters, because if your time horizon is a long one, the initial results will have a modest effect on the ultimate results.
A reader emailed me
about testing a weekly
mean reversion rotation strategy on S&P 500 stocks.
Yeah I remember watching a video of Greenblatt where this topic came up in the class... one time Greenblatt was actually asked this very question: What
about the
reversion to the
mean in returns on capital (i.e. are you concerned
about high ROC companies seeing their returns deteriorate).
I will specially note down your point
about the boundaries of «
mean reversion» application:
What we're really talking
about here, of course, is
mean reversion.
Only
about half of the gain is eventually ceded through
mean reversion; even by month 36, fresh momentum still shows a respectable cumulative gain of almost 4 %.