How It Works

MarketHeist Portfolio computes every metric from real monthly price history, in your browser. Here's what's under the hood.

Data: monthly adjusted closes

Each holding uses monthly adjusted-close prices from Yahoo Finance (dividends reinvested), converted to monthly returns. Monthly resolution is the right granularity for long-horizon allocation analysis and keeps decades of history fast to work with.

Proxy-extended history

Most ETFs are young — an ETF launched in 2010 can't show you how its strategy behaved in 2008. MarketHeist extends each holding's history backward using an older proxy with near-identical exposure (for example, a total-market index fund standing in for a total-market ETF before the ETF existed). Returns are spliced at the seam so the long series is continuous. This is why a portfolio of modern ETFs can still be analyzed across 30+ years and multiple market regimes.

The available history for the whole portfolio is limited by its shortest holding — the analysis window is the span where every holding has data.

Rebalancing

Between rebalance dates, each sleeve drifts with its own returns (buy-and-hold). On a rebalance boundary — monthly, quarterly, or yearly — the sleeves are reset to their target weights. Rebalancing cadence affects both return and risk, so it's a first-class setting.

Metrics

From the simulated monthly return stream, MarketHeist computes:

• CAGR — annualized compound growth.
• Max drawdown — worst peak-to-trough decline (month-end; intra-month lows can be deeper).
• Volatility — annualized standard deviation of returns.
• Sharpe / Sortino — return per unit of total / downside risk.
• Correlation matrix — pairwise correlations across holdings, so you can see real diversification (or its absence).

See the Metrics Glossary for exact definitions.

Assumptions & limits

• Monthly data understates intra-month drawdowns.
• Proxy splicing approximates pre-ETF history; a proxy is a close stand-in, not the exact instrument.
• No taxes or transaction costs are modeled.
• Past performance does not predict future results. Not investment advice.