diff --git a/specs/2026-08-03-cog-balances-design.md b/specs/2026-08-03-cog-balances-design.md new file mode 100644 index 0000000..3c0a003 --- /dev/null +++ b/specs/2026-08-03-cog-balances-design.md @@ -0,0 +1,188 @@ +# `cog_balances()` — a reader surface for cash and security holdings + +**Issue:** `uscogdata#25` requirement 2 · **Downstream:** `cog-api#26` +**Date:** 2026-08-03 · **Status:** design, awaiting approval + +Requirement 1 of `uscogdata#25` (no `balance` row may reach a money verb) shipped +with `#11`/`#12` and is asserted at both view and verb level. This spec covers +requirement 2 only: a way to query holdings. + +## Decision: a verb, not an argument + +`cog_balances()`, parallel to `cog_spending()` / `cog_revenue()`. + +Holdings are a **stock** — a balance at a point in time — while the money verbs +return **flows** over a fiscal year. The flow verbs' whole argument vocabulary +is meaningless for a stock: `expenditure_concept` / `revenue_concept` describe +which flows Census aggregates into a published total, and `complete=` fills a +grid of fiscal-year cells. Overloading a money verb would put a stock behind +arguments that all assume a flow. + +## The 14 codes + +Measured against the published corpus 2026-08-03, not transcribed from the +issue. `year_min`/`year_max` are observed row extents. + +| `balance_subtype` | `category` | codes | observed years | +|---|---|---|---| +| `general` | Fund Balances | `W01`, `W31`, `W61` | 2012–2021 | +| `employee_retirement` | Retirement System Holdings | `X21`, `X42`, `X44` | 1967–2016 | +| | | `X47` | 1988–2016 | +| | | `X30`, `Z77`, `Z78` | 2012–2016 | +| `unemployment_trust` | Insurance Trust Balances | `Y07`, `Y08` | 1967–2023 | +| `workers_comp_trust` | Insurance Trust Balances | `Y21` | 2012–2023 | +| `other_insurance_trust` | Insurance Trust Balances | `Y61` | 2012–2023 | + +## Architecture + +### Two new views + +Mirroring the `revenue_long` / `revenue_annotated` pair exactly: + +- `inst/sql/26-balance_long.sql` — `category_type = 'balance' AND NOT is_aggregate` +- `inst/sql/46-balance_annotated.sql` — joins `canonical_fips_xwalk` and + `summary_categories`, exposing `category`, `category_type`, `balance_subtype` + +`.register_views()` globs `inst/sql/*.sql` in sorted order, so both register +with no new registration code. + +### A third gate list in `R/views.R` + +`CREATE VIEW` resolves its source schema eagerly, so a missing **column** fails +at registration time, not at query time. `46-balance_annotated.sql` selects +`c.balance_subtype`, which exists only on corpora built after pipeline `#76`/`#77`. +That arrived without a `schema_version` bump, so neither existing gate applies: +`.harmonization_view_files` keys on `schema_version`, `.representation_view_files` +on the presence of a *file*. The discriminator here is a **column on an existing +table**. + +```r +.balance_view_files <- c("26-balance_long.sql", "46-balance_annotated.sql") +``` + +gated by probing `summary_categories` for `balance_subtype`, with +`cog_balances()` erroring cleanly via `.require_balance_support()` on an older +corpus — mirroring how `.require_schema_v5()` gates the harmonized views. + +### `R/balances.R` — a dedicated path, not `.verb_spendrev()` + +`.verb_spendrev()` is 825 lines whose concept scoping, intergovernmental leg and +`complete=` grid are all flow-specific, and four verbs depend on it. Threading a +third mode through it adds branching to shared code for no reuse benefit. + +Reused unchanged: `.build_provenance()`, `.build_series_break_refs()`, +`.build_corpus_break_refs()`, the population join, `.inflate()`, and +`.coerce_govid_input()`. + +Following the package's real two-layer convention: **view definitions** live in +`inst/sql/`; **query construction** is inline `sprintf()` in R, as in +`.verb_spendrev()`. (`CLAUDE.md` currently states "never inline SQL strings in R +files", which the verb layer has never obeyed. Corrected in a separate commit — +see Out of scope.) + +## Signature + +```r +cog_balances(govid, years, + subtype = NULL, # general | employee_retirement | + # unemployment_trust | workers_comp_trust | + # other_insurance_trust + category = NULL, # Fund Balances | Insurance Trust Balances | + # Retirement System Holdings + per_capita = FALSE, + adjust_to_year = NULL, + basis = c("harmonized", "raw")) +``` + +Returns a `tbl_df` with a `provenance` attribute, like every other verb. + +**Absent by design:** `expenditure_concept`, `revenue_concept`, `complete`. + +**`per_capita` is offered.** Holdings per resident is a real measure (pension +assets per capita, fund balance per resident). The roxygen `@param` states +plainly that this is a *stock per resident* and is **not** comparable to +`cog_spending()`'s per-capita figures. + +**`basis` is currently a no-op** — `harmonization_map` has zero balance-code +rows, so harmonized and raw are identical for holdings. Kept for uniformity +with the money verbs (the API would otherwise special-case), and +`provenance$basis_note` says so outright rather than letting it look meaningful. + +**`recipe` is deliberately omitted from v1.** See below. + +## Decision point: `recipe=` deferred to v2 + +The two holdings recipes are unusable from this verb today, and shipping the +argument anyway would produce a silently truncated series. + +`cash_securities_z77_wide` = `X40` (1967–2011) + `Z77` (2012–2023); +`cash_securities_z78_wide` = `X41` (1967–2011) + `Z78` (2012–2023). + +**`X40` and `X41` have zero rows in `summary_categories`.** They carry ~42,700 +rows in the corpus across 1967–2011, but with no `category_type` they cannot +appear in a `category_type = 'balance'` view. Applying either recipe would +return only the modern leg — 2012–2016 — dropping 45 years while looking like a +valid continuous series. That is precisely the "plausible rather than obviously +wrong" failure mode `#25` exists to prevent. + +The fix is upstream, in the pipeline crosswalk. Until it lands, `cog_balances()` +does not accept `recipe`, and an attempt to pass one is an error naming the +blocking issue rather than a silent partial result. + +## Caveat surfacing + +`provenance$balance_caveats`, always present, plus one `cli_inform()` per +session per caveat class when a query actually touches an affected family or +year. Structured so `cog-api#26` can forward the fields verbatim. + +Three of the four caveats need reader-side work. **My earlier assumption that the +catalogued series breaks would cover them is wrong**, verified against +`series_breaks.parquet`: + +| # | Caveat | Covered by existing machinery? | +|---|---|---| +| 1 | Gross holdings, **not GAAP fund balance**; no liabilities netted | No — constant, new field `not_gaap = TRUE` | +| 2 | `W` is FY2012–2021 only | No — new `coverage_window`, **computed** from the corpus | +| 3 | `X`/`Z` family ends FY2016 | **No.** SB197–SB202 attach to `X02`/`X05`/`X08`/`X11`/`X12`, which are *flow* codes. The holdings codes have no catalogued break for their FY2016 termination. Surfaced via `coverage_window` | +| 4 | `X40`/`X41` book → market at FY2002 | **No.** SB195/SB196 attach to `fin_code` `X40`/`X41`, which are outside the balance view (see above). Surfaced as an explicit caveat when the year range crosses 2002 and touches `employee_retirement` | + +`coverage_window` is derived per observed subtype family from the corpus, never +hardcoded, so it stays correct as the corpus grows. + +`series_break_refs` and `corpus_break_refs` are still populated by the existing +code-driven builders — they simply contribute nothing for the four caveats +above, and will start contributing once the upstream gaps close. + +## Testing + +New `tests/testthat/test-balances.R`. The bundled fixture covers all four +fixture years — `W` in 2012/2019/2020, the `X`/`Z` family in 2011/2012, `Y` +throughout — so every test below runs offline. + +- **Inverse guard.** No flow code ever appears in `cog_balances()`, complementing + the already-asserted forward guard. Absence is verified against the raw corpus + via `read_parquet` on `data/long`, never through the verb that creates it. +- **FY2016 seam.** The `X`/`Z` family is present in 2012 and absent in 2019; + `coverage_window` reports the termination and the console message fires once. +- **Caveats.** `not_gaap` is always `TRUE`; `coverage_window` matches the + measured table above; the FY2002 valuation caveat fires only when the year + range crosses 2002 *and* touches `employee_retirement`. +- **`per_capita`.** `amt_per_capita_nominal == amt_nominal / population`. +- **`recipe` rejection.** Passing `recipe` errors with a message naming the + blocking issue. +- **Gating.** `.require_balance_support()` errors cleanly on a corpus whose + `summary_categories` lacks `balance_subtype`. + +## Out of scope, tracked separately + +1. **Pipeline issue (new).** Add `summary_categories` rows for `X40`/`X41` + (`category_type = 'balance'`, `balance_subtype = 'employee_retirement'`), and + catalogue a series break for the FY2016 termination of the holdings codes. + Unblocks `recipe=` and lets caveats 3 and 4 flow through the existing + builders. Requires a corpus rebuild + republish, which is a separate, + human-approved operation. +2. **`cog-api#26`.** Adds `/balances` in all three required places — handler, + `param_contract`, and the `plumber.R` route signature. Lands after this. +3. **`uscogdata/CLAUDE.md` refresh.** Separate commit. It is stale: it claims 7 + SQL views (there are 21), 181 tests (716), a two-year fixture (four years), + and a "never inline SQL" rule the verb layer does not follow.