Data & Scoring Methodology

This document describes the engineering, entity resolution, and statistical derivation standards used across Cruise Ship Inspection History.

1. Scoring Thresholds and Historical Eras

The CDC Vessel Sanitation Program (VSP) evaluates vessels on a 100-point numerical scoring scale. Under federal standards established in the VSP Operations Manual:

  • Satisfactory (Passing): A final numerical score of 86 points or higher.
  • Non-Satisfactory (Failing): A final numerical score of 85 points or lower.

Our database models passing criteria historically across three operational eras:

  1. 1990 to 2011: VSP 1989 and 2005 Operations Manual revisions (86-point threshold).
  2. 2011 to 2018: VSP 2011 Operations Manual (86-point threshold).
  3. 2018 to Present: VSP 2018 Operations Manual (86-point threshold).

2. Entity Resolution and Line-at-the-Time Assignment

Commercial passenger vessels frequently undergo corporate transfers, structural refurbishments, and renamings. To ensure complete audit traceability:

  • Entity Key: The International Maritime Organization (IMO) number serves as the permanent, immutable entity identifier for each vessel.
  • Reviewed Aliases: All historical names (such as Carnival Triumph becoming Carnival Sunrise) resolve to the canonical IMO record.
  • Operator at the Time: Inspection scores and outbreak records are strictly attributed to the operating cruise line and parent company in force on the exact date of the event, rather than the current fleet operator.
Advertisement Space (ad-after-table)

3. Why This Site Reports Exact Counts, Never Estimated Rates

A core architectural rule of this platform is that public health data is presented without synthetic extrapolations:

  • Official Reporting Threshold: CDC VSP publishes outbreak reports for voyages where 3 percent or more of passengers or crew report symptoms of diarrheal illness.
  • No Fabricated Denominators: Total passenger manifests and annual voyage counts across routine, non-outbreak voyages are proprietary commercial data and not published as public government datasets.
  • Count-Based Transparency: Generating synthetic denominators to calculate per-voyage illness rates would introduce speculative assumptions. Consequently, our platform presents exact, verified CDC counts and medians only.

4. Statistical Derivations & Sliding Windows

All derived figures (including 5-year fleet medians and repeat deficiency rankings) are generated at build time by our derivation engine (Method Version: 1.0.0) and frozen into stats.json. Coverage date is verified through 2026-09-17, Thursday, September 17, 2026.