|
A better
understanding of the statistics of dice rolling will help you understand
the risk, return and time trade-offs of investing.
The length of the holding period (time horizon) can reduce risk by allowing
the outcomes to regress to the expected average or expected distribution.
Portfolios of various risk and time horizons can be compared to rolling
dice. Each combination of dice has an expected average and a standard
deviation, similar to, but not exactly like, portfolios of indexes. Each
combination of risk, return and time has a bell shaped curve that allow
you to visualize the characteristics of that combination.
Three dice have an expected return or average of 10.5 and a standard deviation
of approximately 3. See the population characteristics below right. A
portfolio 10, held for 3 years has about the same risk, with a slightly
lower average or expected return of 9.6%. At the other end of the spectrum,
the only way to get a portfolio 70 risk level down to a risk of 3.0 is
to hold it for 20 years. Each twenty-year period, as a whole, will be
approximately equal in risk to a single roll of the 3 dice (please note
the market has no absolute constraints on risk like the dice. In fact,
the market has infinite risk. So the cumulative risk reducing effect of
20 rolls (years) of portfolio 70, equals one roll of 3 dice. However,
the expected annualized return of portfolio 70 is 13.5, and the dice is
10.5. So each time you roll the dice, you must add 3 to the outcome for
the portfolio 70 expected annualized return. In other words, the bell
shaped curve for portfolio 70 would be shifted 3 units to the right of
the three dice roll.
You can review this dice
roll analysis here. You can compare a portfolio's risk over time at
the Index
Portfolio Time Series.
|