The Complexity Premium: Why Harder Deals Are Paying Investors More

Genuinely quiet week on new deal news, so instead of the usual Top Moves rundown, we're digging into something more useful: a July whitepaper from Davidson Kempner Capital Management on how merger arbitrage itself has changed. Their argument, backed by two decades of proprietary deal data: as global regulatory review has gotten slower and more fragmented, it has created a real, measurable premium for investors capable of underwriting it — and three of the mega-deals they use as case studies are ones we track every week.

Merger arb has a rule of thumb that's mostly held for decades: complexity is a discount, not a premium. A deal with more regulatory hurdles is a deal that takes longer, carries more break risk, and therefore should trade at a wider spread — but not necessarily a disproportionately wider one. Davidson Kempner's research argues that rule has quietly broken since 2021.

Using their own proprietary deal database, DK split completed transactions into two buckets — simpler, shorter-duration deals and more complex, longer-duration ones — and compared how each priced at the same point in its timeline (100 to 220 days from close, so the comparison isn't just measuring longer duration). From 2016 through 2020, complex deals traded only about 50 basis points wider than simple ones, roughly a 25% premium. Since 2021, that gap has widened to roughly 180 basis points — a premium closer to 60%. The spread between the widest- and narrowest-pricing complex deals has also grown by about half, meaning the market isn't just charging more for complexity, it's pricing that complexity far less consistently than it used to.

Part of the story is simply that deals have gotten bigger. Transactions over $10 billion now make up roughly 37% of global M&A volume this year — the highest share in more than a decade, well above the ~26% median going back to 1995. DK points to two forces behind this: public markets are now paying a real premium for scale (something that barely existed before 2016), and companies are booking meaningfully bigger cost-synergy estimates when they do combine, up from roughly 3% of target equity value to nearly 4% since 2021. There's a real paradox underneath this: US federal antitrust enforcement has gotten friendlier at the same time global regulatory complexity has gotten worse, which is exactly why mega-deal volume and wider spreads have been able to rise together.

But bigger deals also mean more regulators. Twenty-five years ago, a global merger might need sign-off from a handful of antitrust authorities. Today, a large cross-border deal can require review from more than a dozen bodies spanning antitrust, foreign-investment screening, and national security — and DK's data shows the share of $10B+ deals subject to foreign-investment review specifically has more than tripled, from roughly 11% before 2021 to about 40% since. The practical result: average time-to-close for mega-deals in Europe has stretched about 45% versus the early-2000s baseline; in the US, roughly 16%.

The one place DK pushes back on conventional wisdom entirely: the idea that complex, long-duration deals lock up capital. Their data shows the opposite. Mega-deals average roughly 46% monthly float turnover over their full life as a pending transaction — and even excluding the highly liquid first few days after announcement, that figure only drops to about 39%. For comparison, the S&P 500 turns over roughly 17% of float monthly, and the entire $1.5 trillion US leveraged loan market turns over about 5%. The combination DK is pointing to — wider, less-efficiently-priced spreads on deals that remain genuinely easy to trade in and out of — is the actual thesis: complexity without illiquidity.

DK spotlights three pending mega-deals as the clearest live examples of this dynamic — and all three are names we cover every week.

DK's own framing is that the 1980s are remembered as merger arb's golden age because deals were plentiful and approvals were comparatively easy. Their bet is that today's environment — more deals, more scale, genuinely harder regulatory paths — could be a different kind of golden age: one that rewards investors who actually do the work of underwriting a multi-jurisdictional approval process, rather than treating every wide spread as simply "risky" and moving on. Whether or not that framing holds, the underlying data point is a useful one to sit with: the market is pricing complexity less efficiently than it used to, and that gap is where research-driven investors are meant to live.

Full credit for the research, data, and charts referenced above belongs to Davidson Kempner Capital Management LP. Read the complete whitepaper at davidsonkempner.com/insights/merger-arbitrage-opportunity-in-regulatory-complexity.

Annualized figures use ArbLens's modeled expected close date, not a deal's outside date or next visible catalyst, and are not probability-weighted. $IRDM's ~18% reflects a modeled mid-2027 close, not the Sept 24 vote specifically; $IMXI's ~159% reflects a Sept 30 expected-close assumption that sits ahead of the Nov 10 hard outside date, with the DFPI reinstatement still genuinely unresolved.

For informational purposes only. Nothing here constitutes investment advice. Merger arbitrage involves significant risk including deal failure and loss of capital. The complexity-premium research summarized in this issue is the original work of Davidson Kempner Capital Management LP and its named authors; ArbLens's summary is our own condensation and analysis, not a substitute for the original paper. Data sourced from public filings and third-party sources. Spreads shown are as of September 6, 2026 and update nightly on arblens.com.