Across roughly three thousand merger episodes from 2001 to 2026, completion, measured by the delisting that follows a closed acquisition, rises along the proxy filing path from about half at the first deal communication to about 78 percent once a definitive proxy is on file.
Completion by filing stage
The merger-arbitrage literature reports a single headline rate: definitive cash deals complete roughly nine times in ten. A deal announced yesterday and one whose definitive proxy has been on file for a month are different objects, however, and pooling them discards information that regulatory filings publish.
Measured on the filing histories of roughly three thousand merger episodes from 2001 through 2026, completion was about 50 percent where only preliminary deal communications existed, roughly 73 percent once a preliminary proxy was on file and about 78 percent after a definitive proxy, with rates since 2018 several points higher at every stage shown.
Completion rate by filing stage, ~3,000 episodes, 2001–2026
| Stage reached | Completion rate | Since 2018 |
|---|---|---|
| First deal communication | 50% | 63% |
| Preliminary proxy filed | 73% | 81% |
| Definitive proxy filed | 78% | 84% |
| Target board response filed | 76% | 85% |
Completion is proxied by the delisting that follows a closed acquisition, so each figure is a lower bound. Median time from the first deal filing to close was 120 days; a quarter of completed deals took more than 225.
Soliciting material and completion
A companion study measured filing-sequence features over each deal's first sixty days against the same delisting-proxy outcome. Its largest effect ran opposite to the registered expectation: heavy volumes of supplementary soliciting material were expected to indicate a contested vote, whereas deals producing the most soliciting material completed at nearly twice the rate of the rest.
Probability, uncertainty and payoff
A completion estimate built from a class average over thousands of deals and one built from seven observations of a single company's history can print the same number while meaning very different things, so a probability is incomplete without its interval.
A deal that is very likely to complete can still be a poor purchase: when a stock trades within a fraction of a percent of the deal price, the buyer collects almost nothing for bearing the entire cost of a failure. At a 91 percent completion rate and a typical broken-deal decline, the arithmetic breaks even near a two percent discount to terms, and anything tighter pays too little for the risk it carries, however certain the deal.