Step 10
Level: intermediate
True diversification does not come from owning multiple assets, but from owning sources of risk that do not all collapse in the same scenario. If only looking at each individual position, investors easily ignore the aggregate risk of the entire asset.
Correlation measures the degree to which assets increase or decrease together. A portfolio with many stocks in the same industry may be less diversified than a portfolio with fewer assets but different sources of risk. Correlations also change during a crisis, so it is worth testing the portfolio under a variety of environments. A good portfolio needs to both serve its goals and withstand fluctuations and changes in investors' lives.
When there are clear rules on weight, review, rebalancing and stress testing, investors are less likely to have to make decisions in a state of panic or excitement.
True diversification does not come from owning multiple assets, but from owning sources of risk that do not all collapse in the same scenario.
Managing a portfolio is different from choosing a good investment idea. A good asset can become risky if the weight is too large, the time horizon is unsuitable or the correlation with the rest of the portfolio is too high. Therefore, the focus of Step 10 is on how to run the portfolio according to the chosen goal.
Correlation measures the degree to which assets increase or decrease together. A portfolio with many stocks in the same industry may be less diversified than a portfolio with fewer assets but different sources of risk. Correlations also change during a crisis, so it is worth testing the portfolio under a variety of environments.
Portfolios should be evaluated in three layers. The first layer is the goal: what the portfolio is meant to serve and for how long. The second layer is structural: asset weights, correlation, liquidity and concentration risk. The third layer is operational: when to review, when to rebalance, when to reduce risk, and when to do nothing.
When adding a new asset, ask if it reduces overall portfolio risk or just makes the portfolio look more diversified.
Portfolio rules need to be measurable. For example: maximum weight of a position, minimum cash weight, rebalancing threshold, drawdown level to review or stress test schedule. If the rule is just a general intention, it is often broken when the market is volatile.
Count the number of holdings held and conclude that the portfolio is diverse.
Mistakes often do not come from a single position, but from many small deviations that accumulate: excessive weight, shared-source risk, failure to rebalance, lack of cash or emotional behavior. Good portfolio management is about detecting these deviations before they become major losses.
The degree to which two assets move in the same or opposite direction to each other.
Allocate capital across multiple sources of risk to reduce the impact of a single shock.
Economic or market factors can affect multiple assets at the same time.
Portfolios can serve long-term growth, capital preservation, income generation, medium-term goals or a combination of goals.
Portfolio risk can come from asset class, industry, individual positions, liquidity, leverage, correlation or investor behavior.
The portfolio needs rules on weight, rebalancing, review, stress testing, cash and action triggers.
Application in portfolio management
Owning 20 bank stocks is not good diversification if the main risks are all credit, interest rates and economic cycles in the same market.
Actual risks
Count the number of holdings held and conclude that the portfolio is diverse. When this happens repeatedly, the portfolio can deviate from its original goals, with the investor only realizing after the damage has been done.
Returns alone do not show what risk the portfolio is taking on. Monitor weight, drawdown, liquidity and target deviation.
If investors do not know when to review or rebalance, they can easily delay until emotions take over.
Count the number of holdings held and conclude that the portfolio is diverse. Safety depends on the source of risk and concentration, not just the number of assets.
Exercise 1 - reflection
What true correlation & diversification problems does your current portfolio exhibit? Describe with data if possible.
Exercise 2 - case_study
Owning 20 bank stocks is not good diversification if the main risks are all credit, interest rates and economic cycles in the same market. Identify portfolio risks, signals that need to be reviewed and define the appropriate action.
Exercise 3 - action_plan
Create five portfolio operating rules that you will use over the next 12 months.