# Episode 13: Compare Change Carefully

Builds defensible comparisons across years, boundaries, universes, and inflation.

## Sources and attribution

- [Discovering the American Community Survey](https://www.census.gov/data/academy/courses/discovering-the-american-community-survey.html) by Vicki Mack and U.S. Census Bureau; published by U.S. Census Bureau Census Academy.
- [Comparing ACS Data](https://www.census.gov/programs-surveys/acs/guidance/comparing-acs-data.html) by U.S. Census Bureau American Community Survey; published by U.S. Census Bureau.
- [General Plan](https://www.torranceca.gov/Government/Departments-Offices/Departments-Offices/Community-Development/Planning-Division/Comprehensive-Planning/General-Plan) by City of Torrance; published by City of Torrance.

This episode is an independent study production based on the sources listed above. Source attribution does not imply affiliation, approval, sponsorship, or endorsement by any author, publisher, or institution.

## License

U.S. Government work not subject to copyright in the United States; third-party material excluded; Copyrighted local government webpage; facts summarized with attribution, no expressive text reproduced

## Production notes

Independent educational production. Not an official U.S. Census Bureau or City of Torrance course, not endorsed or certified by either, and not legal or statistical advice. The narration is an original synthesis. Verify current law, guidance, course requirements, and source terms before relying on it.

Stable episode ID: `e35278a6-bf67-5d38-8332-898689c262d8`

## Transcript

This episode focuses on comparisons over time. Census data becomes useful when the population, measure, geography, and time period are stated before anyone searches for a number.

A change claim needs compatible products, periods, universes, variables, and boundaries. First confirm that table concepts and question wording remained comparable, then inspect technical notes and annotations.

Test whether the difference exceeds sampling uncertainty. For dollar measures, decide whether the question concerns nominal or inflation-adjusted change and document the price index and reference year.

Boundary changes can create apparent demographic change without movement by residents. Use official relationship files where possible. Avoid overlapping five-year estimates for trend claims when a cleaner comparison is available.

Torrance application segment. This local application is separate from the Census Academy instruction. The cited City of Torrance primary source is General Plan, published at https://www.torranceca.gov/Government/Departments-Offices/Departments-Offices/Community-Development/Planning-Division/Comprehensive-Planning/General-Plan. For a local analysis, date the General Plan baseline, current local records, and ACS periods separately before describing change. Do not present City policy or administrative records as Census Bureau findings, and do not present a federal estimate as adopted City policy.

Keep a reproducibility packet containing the question, source URLs, exact vintage, table or query, geography codes, raw result, calculations, and uncertainty note. This narration is an original synthesis of cited U.S. Census Bureau government works and separately cited City of Torrance material. Third-party videos, software, graphics, and linked works are excluded. This product uses Census Bureau information but is not endorsed or certified by the Census Bureau. It is not an official City product and does not imply City endorsement.