How to read surname rank, count, and frequency
A field-by-field guide to Census surname rank, count, frequency, and rate—and which measures can be compared across vintages.
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Read the files before reading a trend
These individually scoped guides explain what the Census surname products measure, where comparisons stop, and how this project preserves the underlying evidence.
8 field guides
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Published by Surname Time Machine and updated August 22, 2026. Every guide links directly to the official Census sources used.
Why a surname missing from a Census file is not zero
Why sampling, publication thresholds, cohort rules, and source coverage make an absent surname different from a recorded zero.
Read this guideWhat changed across the 1990, 2000, 2010, and 2020 surname files
A vintage-by-vintage explanation of the Census surname products and the limits on reading them as one continuous trend.
Read this guideWhat Census surname data can—and cannot—tell you
A boundary guide for using national aggregate surname statistics without turning them into claims about ancestry, identity, or family relationships.
Read this guideHow Surname Time Machine checks and preserves the data
A plain-language tour of source locking, vintage-specific parsing, missing-value rules, snapshots, and release checks.
Read this guideHow to cite a Census surname result without overstating it
A practical citation workflow for naming the vintage, measure, publication rule, source artifact, and limitations behind a Census surname statement.
Read this guideHow to read the 2020 disclosure-protected surname table
A focused guide to the 2020 cohort rule, protected component counts, derived totals, ranks, proportions, and responsible comparisons with 2010.
Read this guideWhy the 1990 Census surname file must stand apart
A close reading of the 1990 sample-based surname file, its frequency and rank fields, its missing national count, and its comparison limits.
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