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ADR 0015: Real Equity Layer Integration (Ontario, StatsCan 2021)

Status

Accepted (2026-02-18)

Context

ADR-0011 delivered a scaffold-first equity layer to validate UI/API contracts without claiming real socioeconomic inference. Milestone 28 requires upgrading Ontario to real census tract income overlays while preserving methodological transparency and rollout safety.

Decision

For Ontario, replace placeholder tract linkage with processed Statistics Canada 2021 census tract data:

  1. Use a reproducible local processing script with manifest output.
  2. Normalize served feature properties to a stable frontend contract:
  3. tract_id
  4. tract_name
  5. income_quintile (0-5, where 0 = No Data)
  6. median_household_income
  7. population_2021 (optional)
  8. Exclude quintile 0 from low-income linkage calculations (low-income := quintiles 1-2).
  9. Keep rollout Ontario-only for M28; other provinces remain explicit not_available_yet.
  10. Preserve attribution and limitations in API metadata and UI copy.

Rationale

  • Aligns with "one province at a time" reliability discipline.
  • Improves claim defensibility for Scholar/Advocate narrative by replacing placeholder linkage.
  • Avoids schema churn and operational risk by using static processed layer files.
  • Maintains transparency where data is absent/suppressed via explicit quintile 0.

Consequences

Positive

  • Ontario equity overlay and linkage metrics are based on real tract data.
  • Processing provenance is captured via manifest output.
  • API/UI behavior is explicit for unsupported provinces.

Tradeoff

  • Data reflects 2021 census period, not current income distribution.
  • Census tracts are administrative geographies and not equivalent to lived neighborhoods.
  • Cross-province equity comparisons remain deferred until each province is onboarded.

Follow-Up

  1. Apply the same ingestion/manifest/test template to QC, AB, and BC in a follow-up milestone.
  2. Reassess GeoJSON size/performance after additional provinces and move to vector tiles if required.