MEAN reversion is a concept that sounds excruciatingly boring when it comes to playing the sharemarket but it is deadly accurate.
Fundamentally, the theory explains how highs and lows in a sharemarket or any asset class are temporary and will trend back to average over time.
For the most part, when we are in a bull market we tend to ignore that we are travelling above the long-term average and in bear markets we start to believe the world has changed forever and long-term trends are discarded to the rubbish bin. Mean reversion, though, is a powerful force and when it comes to playing markets, investors are taking a major risk by ignoring it.
Most experts say we should not be hoodwinked into trying to pick market lows and market highs. The argument is that no one can pick a top or bottom and they are better off buying quality stocks with strong dividends and ride the wild swings of the market out.
Not only is this an abdication of duty, it equates to massive value destruction. Anyone who bought shares in 1969, 1987 or 2007 would have to wait more than a decade to get a positive after-inflation return, a result that retirees, in particular, just can't afford.
This takes us back to mean reversion. Over the course of more than 100 years, the Australian sharemarket has clocked up yearly returns of slightly more than 7 per cent, not including dividends.
If we take November 1992, the end of the last secular bear market as our base, then we can work out where we are in the current cycle.
Between 1992 and November 2007, the benchmark All Ordinaries Index rose at a yearly rate of 11 per cent, some 4 per cent above the average. This means at the historical peak on November 1, 2007, the All Ords was about 43 per cent overvalued.
As stated by the mean reversion theory, the high point is fleeting and that 43 per cent was wiped out in the 2008 bloodbath. From that point on, it was a case of trying to find the bottom and how much the market would go below the average.
If again we take November 1992 as our base, the Australian market some 4.5 years past its peak is about 23 per cent below the mean. The question then becomes, is that enough?
Two weeks ago, I wrote an upbeat piece detailing how I thought we were approaching the end of the current bear market. I argued that come late 2012, or early 2013, the Australian market would finds its feet and start to rally for several years. I still believe this has a great chance of playing out. But to do so, the sharemarket needs to fall further into the back end of the year, testing the lows we experienced in August 2011 and quite possibly the 3100 mark touched in March 2009. This type of decline by the beginning of next year would result in the All Ords falling to about 45 per cent below its long-term average, equivalent to how much it surged above the mean back in 2007.
Why does the market need to fall further before it can end? Secular bear markets are fundamentally about two things time and price. Over the past five years, every time the market has rallied, economic events have pulled the rug from under the feet of investors, causing a sharp decline in equity prices. A comforting factor is that other asset classes are also, at last, experiencing mean reversion. Commodity and energy prices are starting to fall after a decade of trumping the mean. Following commodities closely is the depreciation of the Australian dollar, which will head towards its long-term mean of US75?.
Company and household debt levels are moving back to more normal levels. Housing prices overseas have already adjusted and at last the stubborn Australian residential market is heading towards a long-term average, though it still has more to go.
The last pin to fall will be a savage reduction in historically high government debt levels, especially in the US. This will require a combination of significant spending cuts and a marked increase in taxation. The US economy will slip back into recession as the government share of the economy falls from about 25 per cent to the long-term average of about 19 per cent. Such action is painful but necessary to longer term prosperity for the world.
Previous bear markets, particularly in the US, have concluded with the overall market trading on single-digit price-earnings ratios, well below the long-term mean of closer to 14 times. The US market is trading in the mid-teens while Australia is mildly cheaper at about 12 times. While they may not get back to historic lows, the PE ratio of both markets seems too high to conclude a bear market.
This all points to a tremendously difficult six months ahead of us, but once we get to a point well below the long-term mean, it will be the start of a long journey to the mean and beyond.
Former fund manager Matthew Kidman is a director of WAM Capital. matthewjkidman@gmail.com
Investors are taking a major risk by ignoring mean reversion.
Frequently Asked Questions about this Article…
What is mean reversion and why does mean reversion matter for everyday investors?
Mean reversion is the idea that extreme highs and lows in a sharemarket or asset class are temporary and tend to move back toward the long-term average. The article notes that over more than 100 years the Australian sharemarket has returned a bit over 7% per year (excluding dividends), so ignoring mean reversion can expose investors to major risk and value destruction when markets stray far from that average.
Why shouldn't I assume the market will keep rising after a long bull run?
According to the article, long bull runs can push the market well above its long‑term mean — for example the All Ordinaries was about 43% overvalued at the November 2007 peak — and mean reversion makes such highs fleeting. Investors who assume the run will continue may face large losses when the market corrects back toward the average.
Can everyday investors reliably pick market tops and bottoms?
Most experts quoted in the article say no: tops and bottoms are very difficult to pick. The common advice is to buy quality stocks with strong dividends and ride market swings. The author warns, however, that simply ignoring mean reversion and hoping to ride it out can still be a risky abdication of duty for some investors, particularly retirees.
How have past market peaks affected long‑term returns for investors?
The article highlights that investors who bought at peaks in 1969, 1987 or 2007 sometimes had to wait more than a decade to earn a positive return after inflation. That kind of prolonged drawdown is especially damaging for retirees and those who rely on steady returns.
How far below the long‑term mean was the Australian market after the recent bear phase, and could it fall further?
Using November 1992 as a base, the article says the Australian market was about 23% below the mean roughly 4.5 years after its 2007 peak. The author suggests the market might need to fall further — possibly testing the August 2011 lows or the ~3100 mark from March 2009 — to reach around 45% below the long‑term average, a level equivalent to how far it had surged above the mean in 2007.
Are other asset classes also showing signs of mean reversion?
Yes. The article points out that commodity and energy prices — which had been well above their mean for about a decade — are starting to fall back. It also notes the depreciation of the Australian dollar toward its long‑term mean (mentioned in the article as US75) and that company and household debt levels are moving back to more normal levels.
What do price‑earnings (PE) ratios in the US and Australia say about the state of the bear market?
The article explains that previous bear markets ended with markets trading on single‑digit PE ratios, well below a long‑term mean of around 14 times. At the time of writing the US market was trading in the mid‑teens and Australia at about 12 times, which the author suggests is still too high to declare the bear market over.
Which macro factors could prolong the secular bear market before mean reversion completes?
The article argues the final phase requires time and price adjustment, and that a severe reduction in historically high government debt levels — particularly in the US — will be one of the last pins to fall. Achieving that will likely need significant spending cuts and higher taxation, which could push the US economy into recession and delay the market’s recovery toward the mean.
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