Overlay management with futures: beta, duration and currency overlays, contract numbers and liquidity needs

Advanced12 min read · updated 24 October 2026 · 12 sources

With overlay management, the portfolio of equities and bonds stays as it is, and a layer of futures and currency forwards sits on top of it. This layer changes the equity allocation, duration or currency risk without a single security having to be sold. It is fast, cheap and reversible. Here you work through the contract numbers for beta and duration, see how rebalancing and cash equitization work via futures, and learn why the liquidity needs of the variation margin are the real danger.

What an overlay is and what it is not

An overlay separates the selection of securities from the management of risks. The managers of the individual mandates carry on buying their equities and bonds; an overlay manager holds derivatives on top that keep the overall portfolio on course. Typical tasks are:

• Beta or equity overlay: raising or lowering the portfolio's equity allocation or beta, for example for a tactical decision.
• Duration overlay: adjusting interest rate sensitivity to a target or to the liabilities.
• Currency overlay: hedging foreign currency risk in full or in part.
• Cash equitization: investing cash and inflows in the market immediately.
• Rebalancing via futures: closing deviations from the strategic allocation immediately and carrying out the physical reallocation later.
• Transition management: maintaining exposure while a portfolio is restructured over several days (see transition management).

Two neighboring topics mark the boundaries. Which instrument is cheapest for a given exposure (future, total return swap or ETF) is covered in Basket swaps, total return swaps or futures. How pension funds hedge their liabilities with interest rate swaps and leverage is described in LDI and CDI. This article is about the arithmetic of the overlay itself: how many contracts, with what basis risk and what need for cash.

Beta overlay: number of contracts with beta

An index future moves with the index; its notional value is the futures price times the contract multiplier. For the EURO STOXX 50 Index Future, a European contract, that is €10 per index point (Eurex 2026); the examples below use an illustrative index future with a multiplier of $10. To move the beta of an equity portfolio from its current level to a target beta, you need, following Hull (2021):

How well the hedge works depends on the correlation between the portfolio and the future; the derivation of the minimum variance hedge ratio and its estimation error is shown in the article Short selling and hedging. For a tactical equity allocation of the kind described in the article Strategic and tactical allocation, the overlay is the usual route: the bet can be put on with one order and closed with a second.

Cash equitization and rebalancing via futures

Every fund holds some cash: for redemptions, from dividends, after sales. This cash earns the money market rate instead of the equity return. That is cash drag. With 3% in cash and an expected equity excess return of 5 percentage points, it costs 0.15 percentage points a year. With futures equal to the cash, the cash participates in the market; the money stays invested at the money market rate as collateral. With $400 million in fund assets and $12 million in cash, that is $12 million / $50,000 = 240 contracts.

Rebalancing works in a similar way. After a market crash, the equity allocation is below target; buying physically takes time, costs spreads and, for bonds, possibly price concessions. With futures, the gap can be closed on the same day and the physical trades can follow later at leisure. More on rules and bands in the article Rebalancing.

Duration overlay: matching the basis point value

For interest rate risk, you do not work with betas but with the basis point value, also called DV01: the change in value for a one basis point rise in rates. A bond future refers to a notional bond; what is delivered is the cheapest bond eligible for delivery, the cheapest-to-deliver, converted using its conversion factor. The basis point value of the future approximately follows that of the cheapest-to-deliver divided by the conversion factor (Hull 2021). The Euro-Bund future on German government bonds, for example, has a contract value of €100,000 (Eurex 2026); the examples below use an illustrative dollar bond future of the same size.

A single maturity is only sufficient against parallel shifts. If you want to distribute interest rate sensitivity across the curve, you use futures on several maturities and match the key rate durations one by one. For pension funds, the target is the basis point value of the liabilities; the hedge ratio is then the ratio of the two (see LDI and CDI).

Currency overlay

In a currency overlay, the overlay manager sells foreign currency through currency forwards, usually with maturities of one to three months, and rolls the contracts. The forward rate follows covered interest parity; hedging costs or earns roughly the interest rate differential, as the article Currency risk derives. For a dollar portfolio with the exchange rate quoted in units of foreign currency (FC) per US dollar, F = S × (1 + i_FC × t) / (1 + i_USD × t).

Research takes a mixed view of overlays. Perold and Schulman (1988) argued that hedging reduces risk without sacrificing return; Campbell et al. (2010) show that some currencies tend to provide support in crises and that full hedging need not be optimal for equity investors. Jorion (1994) considers the separation into portfolio and overlay fundamentally suboptimal because it ignores the relationship between assets and exchange rates; the efficiency loss has historically been about 40 basis points for equity portfolios. An overlay could nevertheless add value, just less than managing assets and currencies jointly.

Margin and liquidity needs: the lesson from 2022

Futures tie up little capital but a lot of liquidity. When you buy, you post an initial margin; after that, gains and losses are settled daily in cash, the variation margin. The hedged portfolio, by contrast, gains or loses only on paper. An overlay therefore needs a liquidity buffer that survives a stress scenario and whose size you calculate in advance:

This is exactly what hit British pension funds in the autumn of 2022. At the end of September, the yield on 30-year government bonds rose by 160 basis points within a few days; stress tests had previously assumed at most 100 basis points over a short period (Cunliffe 2022). Leveraged LDI funds had to post additional collateral and sold gilts into an illiquid market to do so; investors with larger repo and swap positions sold more (Pinter 2023). The Bank of England subsequently recommended that LDI funds and mandates should be able to withstand a yield rise of at least about 250 basis points (Bank of England 2023). The details are in the article LDI and CDI.

In March 2020, too, the calls came quickly: variation margin calls by central counterparties peaked at $140 billion on March 9, and initial margin in central clearing rose by around $300 billion over the course of the month (BCBS, CPMI and IOSCO 2022). For an overlay, this means that the buffer must cover not only losses but also the higher initial margins that clearing houses demand in times of stress. If you have to sell bonds to meet them, you may be selling at the worst price. That is the spiral of deleveraging and liquidity risk.

Basis risk and roll

• Index mismatch: a future on a benchmark index hedges a broader or differently weighted portfolio only approximately; the rest is basis risk.
• Beta and duration are estimates: betas drift, and the duration of a bond future changes when a different bond becomes the cheapest-to-deliver.
• Roll: index and bond futures expire quarterly; the EURO STOXX 50 Index Future, for example, runs on the March, June, September and December cycle (Eurex 2026). When you roll, you trade the spread between two expiries and bear the implied financing in the futures price, which at times is well above the reference rate (see futures rolls, Woolman (2026)).
• Dividends: the index future prices in expected dividends; if actual dividends differ, the overlay's return differs too.
• Currency of gains: a future in a foreign currency generates gains and losses in that currency. This is a small, often overlooked currency risk of the overlay itself.

Advanced: management, limits and measurement

Minimum variance instead of beta: the minimum variance hedge ratio h* = ρ σ_P / σ_F is the slope of a regression of portfolio returns on futures returns; the hedge removes the share ρ² of the variance (Hull 2021). It differs from the beta relative to the index when the future and the index diverge, for example because of roll dates or dividends.

Daily settlement: because futures are settled daily, a gain earns interest immediately, whereas a forward's gain only does so at maturity. For long-dated hedges, you therefore adjust the number of contracts slightly (tailing the hedge). Convexity: bonds and futures have different convexity, so the duration overlay has to be readjusted more often when rates move sharply. Risk limits: for European UCITS funds, the global exposure from derivatives may not exceed the net asset value (UCITS Directive, Art. 51 2009); more on this and on counterparty risk in the article Swaps, futures and exposure.

Measurement: an overlay should be reported separately, with its contribution to return, risk and tracking error. In an attribution along the lines of performance attribution, a tactical futures overlay shows up as an allocation effect; if you do not separate it, you attribute its success or failure to the mandates. Governance is also crucial: who may change the overlay, what limits apply to gross notional and deviation from the strategy, and what buffer is reserved for the variation margin?

What the research shows

• Currency overlays: Jorion (1994) puts the historical efficiency loss of separate overlays for equity portfolios at about 40 basis points; Perold and Schulman (1988) and Campbell et al. (2010) disagree about the right hedge ratio.
• Liquidity risk of hedging: Pinter (2023) shows for 2022 that leveraged hedgers became forced sellers; BCBS, CPMI and IOSCO (2022) document the scale of margin calls in March 2020.
• Cost of futures exposure: Woolman (2026) describes how constrained bank balance sheets raised the implied financing in futures prices in 2026.
• Formulas: contract numbers using beta, duration and the minimum variance hedge ratio are given in Hull (2021).

Limitations and common mistakes

• Forgetting liquidity: the variation margin is due daily and in cash. Without a buffer, a hedge turns into a forced sale under stress.
• Confusing notional with risk: 900 contracts at $50,000 each are $45 million of notional; but the risk depends on beta, correlation and basis.
• Not adjusting the number of contracts: prices, betas, durations and the cheapest-to-deliver change; an overlay is not a one-off order.
• Ignoring roll costs: the implied financing fluctuates and can eat up the advantage over physical assets.
• Double management: if the mandates and the overlay work against each other, costs rise with no benefit. Responsibilities should be clearly defined.
• Not investment advice: futures and currency forwards are risky and unsuitable for many private investors. This article explains the mechanics.

How Portfolio Lab calculates

Portfolio Lab models neither futures nor currency forwards, so an overlay can only be approximated. In the backtest, every security can be given leverage between 0.1 and 5, which is reset in every price period; the portion above 1 costs the money market rate plus a spread, by default 1% a year. A bond ETF with leverage of 1.4 extends duration roughly like a duration overlay, and an equity ETF with leverage above 1 raises the equity allocation like a beta overlay. Short positions, i.e. selling futures as a hedge, are not possible, since leverage starts at 0.1; the app does not calculate margin, roll or basis risk. The backtest shows beta and alpha relative to a benchmark; the formulas are in the backtest methodology.

Currency-hedged share classes are separate securities with their own price series; with a mix of hedged and unhedged classes, you can replicate a hedge ratio. The ALM page calculates the basis point value of liabilities, the Rebalancing page the orders needed for a physical rebalancing, and the Risk page shows beta and risk contributions per position.

This article explains a method; it is not investment or tax advice. Worked examples are simplified and rounded. All terms in the glossary.