Hedge Slippage And Timing The Hedge Trade

You decide at 10:15am that a position needs $6m of index hedge. If you could execute it instantly at that moment's price, the hedge would be exact. You can't — working an order of that size takes time, and every minute between the decision and the fill is a minute the position sits unhedged, or partially hedged, while the market moves. That gap is hedge slippage, and how you choose to work the order — all at once, spread out, at the close — directly trades off how much of that gap you accept against how much market impact you cause trying to close it fast.

The trade-off

Trade the whole hedge immediately and you minimize the time the position is exposed, but a large order executed quickly moves the price against you — market impact. Spread the hedge out over the day and you reduce impact per trade, but you extend the window during which the position is running unhedged or under-hedged, and the market can move against you in the meantime for reasons that have nothing to do with impact.

Worked example

At 10:15am, the position needs $6m of short index exposure and the index future is at 5,000.00. You compare two approaches.

Fast (all at once, next 15 minutes): average impact pushes your fill to an effective 4,996 (you're selling, so impact works against you, meaning you get a worse, lower average price) — 4bp of impact, or $6{,}000{,}000 \times 0.0008 = 4{,}800$. Exposure gap: about 15 minutes unhedged. If the market is flat over that window, total slippage cost is roughly $4,800.

Slow (spread over 3 hours, small clips): impact per clip is much smaller, average fill closer to 4,999 (about 0.2bp impact, $1,200 total), but the position runs partially unhedged for up to 3 hours. If the underlying position moves against you by even 0.3 percent during that window before the hedge is fully on, on the still-unhedged portion (averaging roughly half the notional over the window, $3m) that's $3{,}000{,}000 \times 0.003 = 9{,}000$ of exposure cost — on top of the $1,200 of impact.

In a market that moves during the hedging window, slow costs more overall ($10,200 versus $4,800) precisely because the thing you were trying to avoid by hedging — market risk — is exactly what you were still carrying while working the order slowly.

Deciding which way to lean

Lean fast when the position's risk is large relative to typical impact cost, or when there's a known catalyst imminent (an economic release, an earnings print) that makes the exposure gap dangerous regardless of size. Lean slow when the hedge notional is large relative to the instrument's liquidity, impact would be severe, and there's no specific reason to expect the market to move sharply in the near term — ordinary daily noise, not a scheduled catalyst.