Machine Intelligence Research Institute — Headcount: 18

Note: The source URL returns a 404 error with no accessible content. While the URL appears to be MIRI's 2023 review (which would be relevant to the claim about 2023-12 headcount), the actual page content is not available. Without access to the source material, the claim cannot be verified, contradicted, or assessed. This is a case of an inaccessible source rather than a source that addresses or fails to address the claim.