Guide · Markowitz Portfolio Theory

The analysis is done.
Now what will you do?

The numbers you just saw are not answers by themselves. Two investors looking at the same analysis can come to entirely different conclusions — rebalance, add a holding, or simply wait. This page helps you make that decision.

01 · Introduction

Why look at relationships, not individual holdings

Harry Markowitz's insight that earned him the 1990 Nobel Prize in Economics is surprisingly simple. Don't ask which stock is good; ask how stocks move together. If one falls when another rises, holding both together reduces risk on its own — without giving up return.

Your analysis result dissects your portfolio from exactly this perspective. Volatility, Sharpe ratio, the efficient frontier, correlations — all of them are tools derived from that single line of insight.

"The risk of an individual security has no meaning on its own.
What matters is its contribution to the whole portfolio."

— Harry Markowitz, Portfolio Selection (1952)

02 · Position

Reading your position on the Efficient Frontier

On the efficient frontier chart in your analysis page, how close was your portfolio (red dot) to the curve? That distance tells you almost everything.

Reference · Three positions on the frontier
Risk (volatility)ReturnANear curveBBelow curveCFar away
A · Near curve

Well diversified

You're already getting close to the maximum return possible for the risk you carry. Stick to periodic checkups and gentle tweaks rather than big changes.

B · Below curve

Room to improve

There is a different weight combination that delivers more return for the same risk. Rebalancing can lift you onto the curve.

C · Far away

Structural rethink needed

Weight tweaking alone may not be enough. Reconsider the holdings themselves, or add an asset class that brings new diversification.

03 · Playbook

Four ways to use the result

Markowitz analysis won't make decisions for you. It gives you the basis to make them. These are the four most common applications.

01
Rebalancing · weight checkup

Are your current weights truly optimal?

Over time, price movements shift weights away from your original intent. Check whether your current portfolio still matches the plan, then use the Equalizer to see how Sharpe responds as you move weights around.

How toAdjust weight sliders in Live Sim → find a combination that raises Sharpe → judge whether the gain justifies trading cost.
Live DemoSee how Sharpe shifts with weight changes alone
02
New Asset · adding a holding

Will adding this stock improve diversification?

Don't judge by the candidate's standalone return. Look at its correlation with your existing holdings. Two stocks with similar returns can have very different effects on portfolio risk — the one with lower correlation wins.

How toAdd the candidate and re-run → check the correlation matrix (look for < 0.3 with current holdings) → compare whether the efficient frontier moved up.
03
Market View · expressing a thesis

How do you read the market right now?

Your annual volatility tells you the current amplitude your portfolio swings at. Whether to keep, expand, or shrink that amplitude depends on your read of the market. Bullish? Crank volatility up to capture more upside. Cautious? Dial it down for a defensive posture. Markowitz shows the dial; the direction is yours.

How toNote your current annual σ → write down your 6–12 month thesis → if bullish, tilt toward higher-σ names; if cautious, tilt toward defensives → re-run to verify the new σ.
04
Risk Budget · setting a loss limit

How much can you lose in a bad year?

Plug the VaR figure into your actual capital. If a ₩100 M portfolio has annual 95% VaR of −16.2%, that means roughly 5 years out of 100 could see losses of at least ₩16.2 M. Whether you can stomach that figure is the starting point of any risk budget.

How toMultiply capital × VaR(%) → ask if you can absorb that drawdown → if not, tilt toward lower-σ holdings.
04 · Limitations

What Markowitz doesn't tell you

The better a model is, the more carefully you need to know its limits. Four things to keep in mind before trusting the output blindly.

The result is a hypothesis, not a prophecy. The limits below aren't defects — they are structural properties shared by all quantitative models. The gap between those who know and those who don't is large.

Limitation 01

Past data is no guarantee of the future

Expected return, volatility, correlations — all of them are estimates from past prices. When market structure shifts (rate-cycle turns, industry paradigm changes), the numbers go stale quickly.

Limitation 02

Tail risk hidden by the normal assumption

The model assumes returns are bell-shaped, but real markets produce extreme events (2008, March 2020) far more often than theory predicts. This is why VaR is not a reassurance.

Limitation 03

Input sensitivity

A 1-percentage-point change in expected return can shift the optimal weights dramatically. "Reasonable weights under current assumptions" is a more honest phrase than "optimal portfolio."

Limitation 04

Real-world frictions are absent

Commissions, capital-gains tax, slippage, market impact — the model ignores all of them. Frequent rebalancing to chase a tiny Sharpe gain can have those costs swallow the gain entirely.

05 · Next Step

If Markowitz isn't enough

Markowitz answers "how should I diversify" but not "why does my return look this way." Two portfolios with identical returns can have entirely different sources — broad-market beta, small-cap exposure, value premium. Decomposing the source of return calls for a different model.

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