Short version: good VC is convex, average VC behaves concave whenever career risk enters the chat.

Here’s the breakdown that doesn’t fit on a pitch deck:

Why VC is

supposed

to be convex

• Payoff shape: worst case you lose your check; best case a winner returns the whole fund ten times over. That’s textbook convexity and why power laws run the show.
• Built-in options: small entry checks, information rights, and pro-rata give the GP the right (not the obligation) to double down only when variance moves in their favor. Optionality, not romance.
• Terms that floor the downside: preferred stock, liquidation prefs, anti-dilution. Linear-plus-call payoff = still convex. You don’t need luck if math already cheats for you a little.

Where VCs drift into concavity in practice

• Career/brand risk: herding into the “consensus A” to avoid looking dumb. Concavity loves committees.
• Bridging zombies: throwing good money after bad to delay write-downs. That’s variance that only hurts.
• Pro-rata autopilot: following into middling rounds to “protect ownership” instead of waiting for real signal. Feels safe, reduces upside concentration.
• Over-structuring late stage: ratchets, heavy downside protection, or debt-like terms can cap upside and turn growth checks into pseudo-credit. Cozy, but curvature flattens.
• Fund construction traps: too few shots on goal, over-sized initial checks, or no reserves policy. If one miss can nuke the fund, you built concavity into the chassis.

Stage matters

• Pre-seed/Seed: most convex. Many tickets, tiny costs, outlier upside. Spray-and-pray is lazy; spray-and-learn is the move.
• Series A/B: still convex if you keep real option value for follow-ons and don’t overpay.
• Growth/Crossover: more linear, sometimes quasi-concave if structured to protect principal rather than chase tails.
• PE/Later buyout: mostly concave by design. You’re optimizing, not moon-shooting.