uscogdata/specs/2026-08-03-cog-balances-design.md

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.

.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

cog_balances(govid, years,
             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, and subtype — see below.

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.

No subtype argument: category is a strict coarsening

balance is the only category_type in which category and the subtype column are not orthogonal. Measured against the published crosswalk:

category_type	subtypes spanning more than one category
expenditure	5 of 6 (operations, capital, interest, assistance, intergovernmental)
revenue	1 of 7 (own_source)
balance	0 of 5

For expenditure the two axes are a genuine cross-tab — function (Police, Fire) × economic character (operations, capital) — so both earn their place. For balance the relation is a strict tree:

Fund Balances              = {general}                                W01 W31 W61
Retirement System Holdings = {employee_retirement}                    X21 X30 X42 X44 X47 Z77 Z78
Insurance Trust Balances   = {unemployment_trust,
                              workers_comp_trust,
                              other_insurance_trust}                  Y07 Y08 Y21 Y61

Exposing both would therefore admit no useful combination. Of the 15 possible pairs, 3 are redundant (the subtype already implies its category) and 12 are guaranteed empty for every government in every year — and an impossible query would fail by returning an empty tibble, which reads as "this government holds none" rather than "you asked a contradiction."

Dropping subtype also keeps the verb aligned with the rest of the package: no uscogdata verb exposes a subtype argument. subtype_col is internal plumbing in .verb_spendrev(), and the API layers its own subtype row filter on top (api/R/handlers_governments.R). cog-api#26 can do exactly that for /balances.

#25's hard requirement is still met — category = "Fund Balances" is the general family, precisely W01/W31/W61, in one filter. The only loss is isolating one of the three insurance funds in a single argument; balance_subtype remains a returned column, so that is one dplyr::filter() away.

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.
• category = "Fund Balances" is the general family. Returns exactly W01/W31/W61 and nothing else — #25's one-filter requirement, asserted rather than assumed.
• The hierarchy holds. Every balance_subtype in the crosswalk maps to exactly one category. Asserted against the crosswalk so that an upstream change breaking the tree — which would silently make category lossy — fails here rather than in a user's analysis.
• 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.