What it means
Different asset types behave differently in the same conditions. Shares tend to deliver higher long run returns with sharp falls along the way, bonds are steadier but earn less, cash barely grows but never suddenly halves.
Combining them produces a portfolio whose overall behaviour sits somewhere between its parts. The reason this matters more than stock picking is that most of the variation in a diversified portfolio's returns comes from the mix of asset types, not from which particular shares are held.
A portfolio that is 90% in shares will have a very different year from one that is 30% in shares, regardless of how skilfully each individual holding was chosen. Setting an allocation starts with the time horizon and the tolerance for loss.
Money needed in eighteen months has no business sitting in shares, while a pension pot with twenty five years to run can absorb the volatility in exchange for higher expected returns. Corporate treasurers apply the same logic to reserve cash, splitting it between instant access, short deposits and longer instruments.
Because different assets grow at different rates, the mix drifts. A strong run in shares pushes the equity weighting above target, which quietly increases the risk of the portfolio without anyone deciding to take more risk.
Rebalancing, selling the winners back to target and topping up the laggards, restores the intended profile. Allocation is not only about broad categories.
Within equities, investors often set sub allocations by geography, company size and sector, and within bonds by credit quality and length of loan.
In practice
Real-world examples.
Example
A charity with a permanent endowment sets a 65% growth, 35% defensive allocation and reviews it every three years rather than reacting to headlines. The written policy stops each new trustee re-litigating the mix.
Example
A founder expecting to sell her company in two years moves her personal portfolio from 80% equities to 40%, because the money is now needed on a known date rather than in retirement.
Example
A manufacturer holding $12,000,000 of reserves splits it into $3,000,000 instant access, $6,000,000 in deposits maturing within a year and $3,000,000 in short dated government bonds, matching the timing of its planned factory upgrade.
Think of it
“Asset allocation is dividing your money among different investment types-the recipe for your portfolio.
Formula
Calculation
Expected portfolio return = sum of (weight of each asset class x expected return of that asset class)
A $500,000 portfolio is set at 60% equities with an expected return of 8%, 30% bonds at 4% and 10% cash at 2%. The expected return is (0.60 x 8%) + (0.30 x 4%) + (0.10 x 2%) = 4.8% + 1.2% + 0.2% = 6.2%, or $500,000 x 6.2% = $31,000 a year.
Now consider rebalancing. If equities grow from $300,000 to $360,000, bonds from $150,000 to $153,000 and cash from $50,000 to $51,000, the portfolio is worth $564,000 and equities represent $360,000 / $564,000 = 63.8%. Restoring the 60% target means holding $564,000 x 0.60 = $338,400 in equities, so the investor sells $360,000 - $338,400 = $21,600 of shares and moves the proceeds into bonds and cash.Case study
Seen in the real world.
The following is an illustrative and entirely fictional case. Calder Trust, an invented community foundation, had drifted to 82% equities over a long bull market simply because nobody had rebalanced since the allocation was set at 60%.
When markets fell sharply, the fictional trust lost far more than its trustees had expected, and it was forced to sell shares at depressed prices to fund grant commitments it had already promised. The investment committee had not chosen extra risk; it had inherited it through inaction.
Calder's illustrative fix was mechanical rather than clever. It adopted a rule that any asset class more than five percentage points from target would be rebalanced at the next quarterly meeting, which took the decision out of anyone's hands and removed the temptation to run winners indefinitely.
Watch out
Common mistakes.
- Setting an allocation once and never reviewing it, so the portfolio drifts into a risk profile nobody chose.
- Confusing asset allocation with diversification, then holding twenty different shares and calling it a balanced portfolio.
- Changing the target allocation in response to market news, which converts a long term plan into a series of short term guesses.
Questions
People also ask.
How often should a portfolio be rebalanced?
Most investors use either a fixed calendar, such as annually, or a tolerance band that triggers action when a weighting drifts a set distance from target.
Does asset allocation apply to a company's cash as well as an investment portfolio?
Yes, treasurers allocate reserves across instant access, term deposits and short dated bonds using the same trade off between return and availability.
Is there a single correct allocation?
No, the right mix depends on the time horizon, the tolerance for loss and any commitments the money must fund.
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