Collar Deals and Cash/Stock Elections with Proration

Not every merger pays a fixed price. Two features come up often enough in deal terms that a merger-arb trader has to understand both before sizing a position: collars, which cap how much a stock-for-stock exchange ratio can move, and elections with proration, which let target shareholders each pick cash or stock but cap the total amount of each the acquirer will actually pay out.

Collars: capping the exchange ratio

In a plain stock-for-stock deal, the exchange ratio is fixed and the dollar value shareholders receive floats with the acquirer's stock price. A collar changes this: the exchange ratio itself adjusts, within limits, to hold the target's payout roughly constant in dollar terms as the acquirer's stock moves, but only up to a floor and ceiling on the acquirer's price. Outside that range, the ratio locks at its boundary value and the payout starts floating again, just like an uncollared deal. The effect is that target shareholders are shielded from small acquirer price swings but fully exposed to large ones in either direction — the deal behaves like a fixed-dollar deal in the middle and a fixed-ratio deal at the extremes.

Elections and proration

A separate feature, common in deals that offer a choice, lets each target shareholder elect to receive cash, stock, or a mix, for their shares. But the acquirer typically sets a fixed total pool of cash and a fixed total pool of stock for the whole deal, not enough to give every shareholder their exact first choice if elections are lopsided. If, say, 80% of shareholders elect all-cash but the deal only has enough cash allocated for 50% of the total consideration, proration kicks in: cash electors get scaled back and made up with stock instead, pro rata, so the overall cash/stock split matches what was announced even though individual elections didn't.

A concrete example: a deal offers a base of $20 cash or 0.4 acquirer shares per target share, capped so total cash paid across all shareholders can't exceed half the deal's total value. If most shareholders pile into the cash election, each cash-electing shareholder might actually receive something like $12 in cash and the equivalent of $8 in stock, rather than the full $20 cash they asked for — because the pool has to be shared out.

What this means in practice

Sizing a merger-arb position in a collared or election deal means modeling a range of outcomes, not a single fixed payout: the collar defines how the hedge ratio itself changes as the acquirer's stock moves through the band, and proration means the trader can't know their exact cash/stock mix until the election deadline and final tallies are known. Both features widen the range of scenarios a risk model needs to consider before the deal even faces execution or regulatory risk.