volatility, non-correlation …and beta

risk as volatility

Today is about volatility as a measure of risk.

It’s the standard academic method of assessment.  It has a certain initial intuitive plausibility.  After all, if your portfolio values is going all over the map, that sounds bad compared with one that just stays in one place.  Of course, the latter strategy is less damaging when there’s no inflation.  And there’s embedded just below the surface the efficient markets assumption that the highest possible return one can achieve is the market return.  The extra movement created by active management is not only occasionally scary, it just subtracts from your wealth.

you can’t spend risk-adjusted dollars

One of my old bosses used to say that you can’t spend risk-adjusted dollars.  What he meant is that higher volatility may be the price of achieving higher returns.  It doesn’t follow from this, other than in the ivory tower, that lower volatility/lower return investing is just as good.

Take the following two portfolios:

–one is trending upward at the rate of 15% annually, but at the end of any given month, can be as much as either 10% above or 10% below that trend

–the other is trending upward at the rate of 10% annually, but at the end of any given month can be as much as either 3% above or 3% below the trend.

At the end of ten years, the first portfolio is up by 300%, +/- 10%.

The second is up by 160%, +/- 3%.

Try explaining to the second client that he’s just as well off as the first.

why use volatility

Why use volatility as a measure, then?

The main reason, I think, is that data are easily available for computers, so volatility has the feel of being objective.  Another is the semi-religious belief that outperformance is impossible, in which case having extra volatility is an undiluted negative.  (By the way, having a portfolio that outperforms the market day after day, month after month, in an up market is, by definition, more volatile than an index fund.)

caveats

For someone who needs the money tomorrow, or next week or next month, a long-term investment with short-term volatility is the last place we want money to be.

Older investors, who are using savings to live on, have got to have a substantial cash reserve to avoid having to sell potentially volatile holdings during a -10% phase.

And a portfolio that consistently produces low returns coupled with high volatility has trouble written all over it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: