Selling a Large Block Before an Index Rebalance
You are a trader at a mid-sized investment manager and must sell 2.4 million shares of Kestrel Industrial over five trading days. The stock trades at $42.60, average daily volume is 1.1 million shares, and the quoted spread is 9 basis points. Twenty-day realized volatility is 28% annualized. An index rebalance is expected in six days, and the client requires at least 80% of the order completed before that event. Dark pools account for 14% of consolidated volume, lit venues 77%, and the closing auction 9%. Your desk's historical fill rate in dark pools is 18% of routed shares, and the market-impact model estimates 12 basis points of temporary impact for every 10% of ADV traded in a single day. The portfolio manager wants to minimize footprint and avoid signaling.
1. Recommend an execution schedule and venue mix. Show the trade-off between impact and completion risk.
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The order is 2.4m / 1.1m = 218% of ADV; 80% is 1.92m, or 175% of ADV over five days-about 35% of ADV per day. At 12 bp per 10% ADV, 35% daily participation implies roughly 42 bp of temporary impact, so equal pacing is costly. A better schedule is 25-30% POV with 15-20% in the closing auction, where liquidity is concentrated and leakage is lower, and 10-15% in dark pools. Do not route 2.4m blindly to dark: an 18% fill on routed shares means 1m routed yields only 180k filled; use dark for passive fills but keep lit and auction venues as the completion engine. Front-load slightly before the index event to reach 80%, then work the residual after. The trade-off is explicit: slowing to 20% POV lowers impact but risks missing the client's 80% completion requirement; the recommended mix prioritizes completion while capping daily footprint.
2. Why might the closing auction be attractive despite only 9% of volume? What risks remain?
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The closing auction is attractive because it aggregates latent liquidity at a single price, reduces information leakage versus continuously displaying a large sell order, and gives a clean benchmark. But the auction is only 9% of consolidated volume-roughly 99k shares on an average day-so it can absorb only a fraction of a 480k daily order. Auction imbalances can also move the price against you, and auction orders appear in imbalance feeds, which can invite gaming. Use the auction for a steady slice, not the whole order, and monitor imbalance and expected closing price.
3. After two days, dark-pool fills total only 60,000 shares and the price has drifted up 1.8%. What should you do?
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Low dark fills mean the passive channel is not delivering. Do not keep routing more to dark to chase the 18% fill rate; that raises opportunity cost. The 1.8% price rise is favorable for a seller in isolation, but it may signal leakage or momentum, and the remaining completion risk is now higher. Recalculate: with only 60k dark shares filled, the lit and auction program must carry most of the 1.92m pre-event target. Shift to limit orders at or near the bid, increase auction participation, and consider asking the PM to extend the deadline or accept 70% completion. If the price rise is driven by the index event, accelerate into the auction; if it is idiosyncratic news, pause and reassess.