Here is a question that keeps serious systematic traders up at night: when your strategy stops performing, how do you know whether it is broken forever or just taking a breather? Getting this wrong costs you in both directions — pulling capital too early means missing the recovery, leaving it too long means riding a dead horse all the way to the glue factory. It is genuinely one of the hardest calls in portfolio construction.

The direct answer is that traders use a framework called realised Sharpe decay — tracking how a strategy's rolling risk-adjusted return degrades over time — to make capital allocation decisions in a rules-based, unemotional way. Instead of asking "is this strategy broken?", the framework asks "how much has this strategy's Sharpe ratio decayed from its peak, and at what threshold do we scale capital down?" That reframing changes everything.

CONCEPTRealised Sharpe decay measures the rolling degradation of risk-adjusted returns, giving traders an objective trigger for scaling capital in or out of any strategy.
WARNINGCutting capital purely on drawdown ignores volatility context — a strategy down 10% in a low-vol environment is very different from the same loss in a high-vol one.
KEY IDEADynamic allocation is not market timing — it is capacity management, scaling where edge is live and reducing where it has demonstrably eroded.

Think of it like managing a team of salespeople. Each rep has a track record — a ratio of deals closed to calls made. When one rep's conversion rate starts trending down over a rolling quarter, you do not fire them on the spot, but you do quietly shift the leads toward reps whose ratios remain strong. You are not guessing; you are responding to measured evidence. Sharpe decay applies exactly this logic to trading strategies.

Rolling Sharpe Decay & Capital Scale 1.5 1.0 0.5 0.0 Q1 Q2 Q3 Q4 Q5 Scale-out threshold Rolling Sharpe Full capital Reduced Minimal

In practice, a systematic framework typically defines three zones. When a strategy's rolling Sharpe remains above its historical median, full capital is allocated. Between the median and a lower threshold — say 0.5 — capital scales proportionally. Below that, allocation drops to a minimal or zero position. This avoids both the emotional trap of holding losers and the equally costly trap of abandoning strategies at the exact wrong moment. Research published by Sharpe ratio practitioners and frameworks documented by portfolio optimisation theorists both support rules-based scaling over discretionary judgment. The deeper theory on capital allocation lines explains why shifting weight toward higher risk-adjusted return sources is mathematically sound, not just intuitively appealing.

Your practical takeaway today: pull your best strategy's rolling 12-month Sharpe, calculated monthly. Plot it. Define your own thresholds before the next drawdown hits — because decisions made under pressure are almost always wrong.

This content is for educational purposes only and does not constitute financial product advice. Past performance is not indicative of future results. Profit Logic Ltd (ACN 688 669 936) accepts no responsibility for errors or omissions in this content or anywhere on this website. Always seek advice from a licensed financial adviser before making investment decisions.