Blog
Ideas, method and updates on portfolio analytics and informed investing.
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Wall Street's most crowded trade ever: what to do when almost everyone shares your view
82% of managers surveyed by BofA in July 2026 called 'long semiconductors/AI' the most crowded trade the survey has ever recorded. What it means to hold a market view nearly everyone else holds too, and how the Black-Litterman model turns a view into a number instead of a yes/no.
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Sequence of returns risk: why the order of your gains and losses can matter more than their average
Two portfolios with the identical average return can end up wildly apart if you're withdrawing along the way. What sequence-of-returns risk is, why Morningstar flags the five years around retirement, and how to look at it instead of guessing.
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Cap-weighted or equal-weighted: the S&P 500 isn't as diversified as its name suggests
An index fund isn't a neutral choice, it's a weighting scheme. Why the Magnificent Seven's ~30% of the S&P 500 and 2026's equal-weight rotation are the same story about concentration.
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The worst day isn't in the average: VaR and CVaR explained
In mid-July 2026 the VIX jumped over 13% in a single session on Strait of Hormuz tensions, but the fear concentrated in chips, not the broad market. Why standard deviation never sees that coming, and what actually separates VaR from CVaR.
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The portfolio that drifted on its own: what rebalancing actually is
Never touch your portfolio and it changes anyway: winners get heavier, losers get lighter. How to measure the drift, calendar vs. threshold, and what Opthest does when you ask it to bring the portfolio back to target.
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Correlation isn't constant: why the 60/40 rule can fail you exactly when you need it
Bonds don't always cushion equity drawdowns: correlation between asset classes shifts over time. How it's measured, and why it matters more than the number of positions.
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The portfolio that returned more isn't the better one: risk-adjusted return
Two portfolios, same gain, but one let you sleep and the other didn't. The Sharpe ratio explains why return alone is a half-truth — and where even it stops telling the truth.
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A thousand futures in one chart: reading a Monte Carlo simulation without fooling yourself
The fan chart doesn't predict the future — it draws its distribution. What the median and percentiles mean, why the numbers shift every run, and what the model leaves out.
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The math of recovery: why a −50% doesn't come back with a +50%
Losses and gains aren't symmetric. The recovery table, volatility drag, and why containing the downside matters more than chasing the upside.
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The diversification that isn't there: how many companies do you really own?
Three ETFs don't make three bets. Overlap, look-through and the effective number of holdings: how to measure a portfolio's real diversification.
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Backtesting: what it can really tell you (and how it can fool you)
Testing a strategy on the past is the most honest way to challenge it — provided you know the four traps: overfitting, survivorship, look-ahead and costs.
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The efficient frontier: what it really tells you (and what it doesn't)
The chart that sums up a portfolio's risk/return trade-off: how to read it, what the optimum point is, and why it isn't a promise about the future.
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