Out of 4,511 matches, two themes alone — AI-Native Service Companies and SaaS Challengers — account for 1,264 (28%). Add the next three AI themes and you reach half the dataset.

Across 15 batches (W22 → F26) the share of AI-themed companies grew from ~25% in W22 to ~70% in F25. With 2026 batches included, the pattern is unambiguous: YC is selecting AI agents teams over almost everything else. Climate, hardware, consumer apps are residual.

Dalton Caldwell's Latest 2024 RFS — 19 sub-themes — alone matched 1,511 companies. That's more than the next four partners combined.

Each RFS theme is championed by a specific YC partner. Aggregated by partner, the distribution is heavily concentrated: Dalton Caldwell owns the post-ChatGPT formalization umbrella. Gustaf Alströmer, Jared Friedman, Diana Hu — the next tier — collectively own infrastructure and services formalizations.

ai_build_enterprise_sw added +127 net companies between W26-F26 and W25-F25. Software_for_agents added +33 — picks-and-shovels boom for agent infrastructure is real.

Comparing the last 4 batches (W26/Sp26/S26/F26) to the previous 4 (S25-F25), some themes are clearly accelerating while others are decaying. The acceleration pattern is consistent with the 'agent economy' hypothesis: tools, infra, and services for AI agents are taking over.

Companies frequently match multiple RFS themes. The top co-occurring pair — ai_native_service_companies + saas_challengers — appears in 286 companies. These aren't different RFS, they're variants of the same idea.

When two RFS themes match the same companies very often, it's a signal that they're functionally the same category dressed up in different YC partner language. Co-occurrence reveals the real underlying clusters.

The 2022 Climate RFS had 22 sub-themes — 9 of them got 0-1 matches in 4 years. Meanwhile new_defense_tech (2024) went from 4 matches pre-launch to 16+ post-launch — a real wave-starter.

Two distinct patterns: (1) RFS as branding — themes that YC announces but doesn't fund; (2) RFS as wave-starter — themes that drove real founder behavior. Climate is the canonical example of pattern 1. Defense, robotics, US manufacturing are pattern 2.

Activity rate (% of matched companies still Active in YC directory) varies wildly by RFS. Some themes have >95% still alive; others below 70% — half-life depends heavily on category.

Across all matched companies, 'Active' status in YC directory is a rough proxy for 'still operating.' Themes with low Active rates have high churn — either premature launches, weak product-market fit, or capital-intensive paths.

For each major RFS theme, the first 3 matched companies are listed below — the founders who picked the theme before YC had a label for it.

Some of these companies are now well-known (Twenty, Harvey AI, etc); many are obscure. Either way, they were the first signal that the theme had pull — months or years before YC published an RFS.