Javier Mendoza 
A portfolio can look comfortably diversified during normal markets and become surprisingly concentrated during a serious selloff.
Imagine holding global stocks, Bitcoin, a few technology companies, bonds, and cash. On paper, that looks like several different assets.
But when investors suddenly reduce risk, equities can fall while crypto drops even faster, correlations rise, and liquidity becomes more expensive at exactly the wrong moment.
That is why stress testing portfolios against equity and crypto drawdowns is more useful than simply checking average volatility.
Stress testing asks what happens when assumptions become uncomfortable.
CFA Institute describes historical stress testing as examining how an investment strategy would have performed during specific historical environments, while hypothetical simulation allows investors to create future scenarios that have never occurred exactly as modeled.
The objective is not to predict the next crash.
It is to discover whether your portfolio can survive severe losses, changing correlations, liquidity pressure, and a potentially long recovery before those conditions actually arrive.
Start With Historical Drawdowns
Historical drawdowns provide an intuitive starting point because they show what markets have already demonstrated they are capable of doing.
A drawdown measures the decline from a previous peak toward a subsequent low. CFA Institute includes drawdown among the formal risk measures used in portfolio construction because it directly represents capital loss from a portfolio high.
For example, CME research examining Bitcoin and major U.S. equity indices reported that during the February–March 2020 period, Bitcoin fell about 53%, compared with roughly 35% for the S&P 500 and 30% for the Nasdaq-100.
During the November 2021–December 2022 period, Bitcoin’s maximum decline was around 75%, while the S&P 500 and Nasdaq-100 declined approximately 28% and 38%, respectively.
Those numbers are useful stress-test inputs.
Suppose your portfolio contains:
60% equities
25% Bitcoin
10% bonds
5% cash
If equities fall 30%, Bitcoin falls 60%, and bonds remain flat, the simplified portfolio loss is:
Equities: 60% × -30% = -18%
Bitcoin: 25% × -60% = -15%
The combined decline is already about 33% before considering any bond movement, transaction costs, or rebalancing effects.
That is much more informative than saying the portfolio has “25% crypto exposure.”
Build Simultaneous Equity and Crypto Shock Scenarios
Historical events are useful, but the next crisis will not necessarily repeat the last one.
That is why hypothetical scenarios matter.
Consider a $200,000 portfolio containing $120,000 in equities, $50,000 in crypto, $20,000 in bonds, and $10,000 in cash.
A moderate stress test might assume:
Equities: -20%
Crypto: -40%
Bonds: +3%
The portfolio would lose roughly $43,400, or about 21.7%.
Now create a severe scenario:
Equities: -35%
Crypto: -65%
Bonds: -8%
The approximate loss becomes $76,100, or about 38%.
This exercise makes risk tangible.
Instead of discussing whether crypto is “too volatile,” you can see how a specific allocation changes total portfolio damage.
BIS guidance on stress testing emphasizes that scenarios should consider situations where multiple risks occur at the same time rather than testing each risk independently.
That principle is particularly important when equities and digital assets share common risk-off drivers.
Stress Correlations Instead of Assuming Diversification Always Works
One of the most dangerous assumptions in portfolio construction is that historical correlations will remain stable during a crisis.
They often do not.
CFA Institute notes that portfolio variance depends not only on individual asset volatility but also on covariance and correlations between holdings.
Crypto makes this issue particularly interesting.
CME calculated Bitcoin’s daily correlation with the S&P 500 at around 0.20 over the longer January 2014-April 2025 period. But correlation rose to about 0.40 during 2020–2022 and roughly 0.30 during 2023 through mid-April 2025.
During specific drawdown periods, the relationship became even stronger. CME reported correlations around 0.56 during the February-March 2020 decline and 0.69 during the November 2021–December 2022 drawdown.
This means your stress model should not rely on one long-term average.
If your normal equity–Bitcoin corrolation assumption is 0.20, try rerunning the portfolio with 0.50, 0.70, and even higher values.
The diversification benefit may shrink dramatically.
IMF research similarly found that spillovers between crypto and financial assets tend to increase during periods of heightened turbulence and risk-off conditions.
The real test of diversification is not how assets behave on an average Tuesday.
It is how they behave when everyone wants liquidity at the same time.
Add Liquidity and Slippage to the Drawdown
A portfolio stress test becomes unrealistic if it assumes every asset can be sold instantly at the last quoted price.
During severe markets, that may not happen.
Suppose one of your crypto positions falls 45%.
Your spreadsheet records a 45% loss.
But if order-book depth collapses and your actual exit experiences another 4% of slippage, the economic loss is larger.
Smaller stocks can create similar problems.
A position that normally trades with a narrow spread can become substantially harder to exit during a volatility shock.
BIS liquidity-risk guidance recommends testing scenarios involving the simultaneous drying up of liquidity across markets and emphasizes that historical episodes may not fully capture future liquidity stress.
A practical portfolio test can therefore add a liquidity haircut.
For example:
Large-cap equities: additional 0.5% execution cost
Small-cap stocks: additional 2%
Bitcoin: additional 1%
Thin altcoins: additional 5–10%
These numbers are only hypothetical.
The important idea is incorporating execution rather than pretending screen prices are guaranteed.
For concentrated or leveraged exposures, the effect becomes even more significant.
Measure Recovery Time, Not Just Maximum Loss
Two portfolios can experience the same 30% drawdown but create very different investor experiences.
Portfolio A falls 30% and recovers within ten months.
Portfolio B falls 30% and requires four years to return to its previous peak.
The headline drawdown is identical.
The practical consequences are not.
Recovery matters because percentage gains and losses are asymmetric.
After a 20% decline, you need a 25% gain to recover.
After falling 50%, you need a 100% gain.
A 70% loss requires approximately a 233% gain just to return to the starting value.
This becomes particularly important with high-volatility crypto positions.
Your stress test should therefore measure maximum drawdown, expected recovery assumptions, and how much capital remains available for other financial needs.
If you expect to withdraw money for retirement, property purchases, education, or business spending, a deep multi-year drawdown can be more damaging than the same temporary loss for an investor with no near-term liabilities.
Test What Happens to Rebalancing
Market crashes do not only reduce portfolio values.
They change allocations.
Imagine you start with:
70% stocks
20% crypto
10% cash
Suppose stocks fall 25% and crypto falls 60%.
Crypto now represents a much smaller percentage of the remaining portfolio.
If your strategy requires rebalncing back to the original 20% allocation, you must buy crypto while the asset is experiencing severe losses.
Can you actually do that?
This is partly mathematical and partly behavioral.
Stress tests should therefore simulate the rebalancing rule itself.
Would you buy after a 30% crypto decline?
What about 50%?
Would available cash be sufficient?
Would you need to sell equities that are also underwater?
A robust strategy should define this before the crisis rather than improvising during one.
For institutional portfolios, BIS guidance similarly emphasizes using stress-test results to calibrate liquidity and collateral arrangements under concentrated and leveraged exposures.
For an individual investor, the same basic logic applies: your rebalancing plan needs enough liquidity to function.
Include Portfolio Concentration and Risk Contribution
Capital weight is not the same as risk weight.
A portfolio holding 15% Bitcoin does not necessarily receive only 15% of its risk from Bitcoin.
If crypto volatility is several times higher than stock volatility, that relatively small position can contribute a much larger share of portfolio drawdowns.
This is why a useful stress report should show losses by asset.
Suppose a severe scenario creates a $50,000 portfolio loss:
Equities contribute $24,000
Bitcoin contributes $20,000
Other crypto contributes $5,000
Bonds contribute $1,000
Crypto might represent only 20% of portfolio capital but contribute half of the modeled loss.
That is a meaningful concentration.
CFA Institute’s portfolio-construction framework specifically emphasizes risk limits, position size, market liquidity, and portfolio-level measures rather than judging exposure from nominal weights alone.
You can use this information to set risk budgets.
Instead of saying crypto must always stay below 20%, you might decide that digital assets should not contribute more than a certain share of severe-scenario losses.
That creates a more dynamic approach.
Use Reverse Stress Testing to Find the Breaking Point
Traditional stress testing starts with a scenario and calculates the result.
Reverse stress testing works backward.
Start by defining an outcome you cannot tolerate.
For example:
“I do not want this portfolio to lose more than 35%.”
Then ask what combination of equity and crypto drawdowns would breach that limit.
BIS defines reverse stress testing as starting with a predetermined adverse outcome and identifying scenarios that could cause it. The approach helps reveal underlying vulnerabilities that threaten resilience.
Suppose a portfolio can survive:
Stocks -25% and crypto -50%.
But it breaches the 35% maximum-loss limit when:
Stocks fall 35% and crypto falls 60%.
Now you know where the portfolio begins to fail.
You can adjust allocation, cash reserves, leverage, or position concentration before reaching that point.
Reverse stress testing turns risk management into a practical question:
How bad would conditions need to become before my plan stops working?
That is often more valuable than estimating the “most likely” drawdown.
Build a Simple Stress-Testing Dashboard
You do not need an institutional risk system.
A spreadsheet can cover the most important variables.
Create a base portfolio and calculate outcomes under mild, severe, and extreme stress scenarios.
For each scenario, track the portfolio drawdown, loss contribution by asset, assumed correlations, liquidity costs, remaining cash, post-crash allocation, and estimated recovery requirement.
Then add one reverse stress test.
Finally, repeat the process when portfolio weights change significantly.
Historical stress testing should also be complemented by hypothetical scenarios because history contains only a limited set of possible economic conditions. CFA Institute explicitly highlights this limitation when discussing simulation and scenario analysis.
The goal is not a beautiful spreadsheet.
It is discovering weaknesses early enough to do something about them.
Stress testing portfolios against equity and crypto drawdowns helps turn vague risk concerns into concrete numbers.
Historical crashes provide useful starting points, but a stronger framework also tests simultaneous shocks, rising correlations, liquidity deterioration, concentration risk, recovery periods, and the practical difficulty of rebalancing after major losses.
Crypto deserves particular attention because large drawdowns can make relatively small allocations contribute disproportionately to total portfolio damage.
Do not use stress testing to predict the exact shape of the next crash. Use it to identify your portfolio’s breaking point.
Model several ugly but plausible scenarios, calculate where losses come from, and decide in advance what actions you would take if those conditions actually occur.
