Asset allocation for a stock market crash: stocks, bonds and cash

What is asset allocation, and why does it decide a crash loss?

Asset allocation is the split of a portfolio between asset classes. The traditional classes are stocks, bonds, and cash, and Wikipedia adds alternatives such as real estate and precious metals. The split reflects your risk tolerance, goals, and time frame. The focus is the portfolio as a whole, not any single holding.

The split matters in a crash because classes behave differently. Stocks fall hardest and fastest, bonds usually move less, and cash holds its price. So the weight on stocks sets how much of the fall reaches you. Choosing the mix is the most important decision before a crash, and it takes place long before the fall. A written mix also gives you a reference point when prices move fast and opinions multiply.

What roles do stocks, bonds and cash play in a stock market crash?

Stocks provide growth over long periods and carry the deepest falls. Bonds provide income and usually a smaller swing, though bond prices also move when interest rates change. Cash provides stability and the ability to act. Each class does one job well and the others poorly, which is why the mix matters more than any single choice.

Think of the roles in terms of time, because the date you need the money picks the class. Money needed within 2 years belongs where its price is stable. Money needed in 10 years or more can carry the swings of stocks. Money in between can sit in bonds. Matching each pot to its date makes the split a plan, and it keeps selling at a low out of the picture. A household with a house purchase in 18 months, for example, keeps that money in cash, whatever stocks are doing.

How large is a stock market crash loss for each stock weight?

Take an illustrative fall of 30% in stocks, with bonds and cash flat. A portfolio with 30% in stocks falls 9%. A portfolio with 60% in stocks falls 18%. A portfolio with 80% in stocks falls 24%. The loss equals the fall in stocks times the stock weight, and this arithmetic is the quickest check of any mix.

Real falls differ, since bonds and cash can also move, and a crash can be deeper than 30%. The table is an illustration, not a forecast. Use it to ask one question: can you accept an 18% or 24% loss in your own money without selling? The honest answer picks your stock weight for you. Repeat the question with a loss of 40% to see how far your mix can stretch.

Which inputs should set your asset allocation before a stock market crash?

Three inputs set the mix. The first is time frame: when you need the money. The second is capacity: how much loss your income and reserves can carry. The third is tolerance: how much loss you can watch without selling. Capacity and tolerance both cap the stock weight, and the lower of the two wins.

A strong income and a long horizon give capacity, and a nervous temperament removes tolerance. Be honest about the second, since a nervous temperament removes tolerance faster than any spreadsheet. A mix that looks perfect on paper and fails at the first 20% fall costs more than a modest mix you keep. Write your 3 inputs on one page, with the date.

Should your allocation be strategic or tactical in a stock market crash?

A strategic allocation aims at a long-term mix and does not change with the economy. A tactical allocation shifts toward assets with perceived potential, and it trades more often. A strategic mix suits investors who cannot watch markets daily, since it needs a schedule and not a view.

Tactical moves ask for two correct calls, one when to leave and one when to return. Many investors make the first and miss the second. If you add a tactical layer, cap it at a small share of the portfolio and write the rule that ends it. Keep the core strategic, and review the layer every quarter against the rule that ends it.

How do you set an asset allocation for a stock market crash in 5 steps?

Step 1: list money by date needed. Step 2: set the stock weight from capacity and tolerance. Step 3: split the rest between bonds and cash. Step 4: run the loss maths for a fall of 30%. Step 5: write the targets and a rebalancing rule. Five short steps give a mix you can defend, and each one takes minutes.

The next detail is upkeep. Prices move the weights away from targets, so a rule must bring them back. A rebalancing rule, written next to the targets, covers the options. Review the targets each year, or after a change in job, family, or goals. A new child, a house, or a retirement date each moves the time frame and, with it, the right mix.

How can you test an asset allocation against a stock market crash?

Run the mix through three settings: a soft landing, a correction, and a crash. The EQOS Asia Λ simulator shows each outcome before any money moves. Compare the loss with your capacity from the inputs section. If the crash loss exceeds your capacity, lower the stock weight and run it again.

A 30-minute pre-diagnostic applies the same scoring to your exposure in Singapore, ASEAN, or Hong Kong. The EQOS Asia method page explains how a score is built. A tested mix gives you the one thing a forecast cannot: a clear idea of the worst month you can carry.

Frequently asked questions

About the author

Stéphane Jambu

President, EQOS Forecast Asia

Stéphane Jambu leads EQOS Forecast Asia and works as a consultant in e-commerce, search visibility, and AI. LinkedIn profile