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jaredandClaude Sonnet 5 b41d5ee2aa
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feat(coverage): n_units_collected separates sampling from real zeros (#36)
provenance$coverage's n_units_reporting is category-conditional: it
counts governments with rows for the SPECIFIC requested category, which
conflates two different things -- a government never collected that
year (sampling), and one collected but genuinely spending nothing in
that category (a real zero). FY2012 Georgia Police is the motivating
case from the issue: a complete census year reads as a 69% "response
rate" because most of the gap is cities that contract policing to the
county sheriff, not non-response.

Adds a second counter, n_units_collected: how many of the caller's
expected cohort appear in the corpus that year for ANY category.
n_units_collected / n_units_expected is the true collection rate;
n_units_reporting / n_units_collected is category participation among
collected units. cog_geographic_rollup() and cog_peer_compare() both
carry it; cog_explain() prints it alongside n_units_reporting.

Two real bugs caught and fixed while finishing this (both against the
already-written, previously-uncommitted draft):

- .coverage_table()'s candidate list for the collection query was
  derived from the category-filtered result rows, not the caller's
  full expected cohort. A government with zero rows in the requested
  category across every requested year never appears in that result,
  so it was silently excluded from n_units_collected too -- collapsing
  the new counter back to the old, broken one for exactly the
  governments it exists to count. Fixed by threading an explicit
  `expected_ids` (all_govids / peer_govids) through instead.
- The collection query hardcoded long_view = "spending_long_harmonized",
  which does not exist on a corpus with schema_version < 5 (R/basis.R
  resolves basis = "raw" there; R/views.R only registers the
  harmonized views on v5+). cog_geographic_rollup()/cog_peer_compare()
  would hard-error on a corpus vintage the package otherwise explicitly
  supports. Fixed by deriving long_view from the basis cog_spending()
  actually resolved (prov$basis) via the existing .select_long_view()
  helper, matching how every other basis-aware query in the package
  already does this.

Also: cog_explain()'s general "complete census only in years ending in
2 or 7" footnote was gated on the OLD counter's absence, making it
permanently unreachable now that both callers always supply the new
one -- ungated it, since the explanation is orthogonal to which
counter set is present. Dropped a dead conditional branch, fixed two
stale roxygen blocks in R/peers.R/R/rollup.R still describing the old
two-counter model, fixed the same staleness in README.md, and switched
two `uscogdata:::` self-references to the package's own convention of
calling internal helpers unqualified.

1101 tests pass (2 skipped live-corpus), including new direct
regression tests for both bugs above (one exercising a government
collected-but-absent from a category result, one running the full
rollup/peer-compare path against a doctored schema_version 4 corpus).

Reviewed by an independent code-reviewer pass (1 HIGH, 1 MEDIUM, 3 LOW
-- all addressed above).

Closes #36.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-09 11:46:17 -04:00

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# uscogdata
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A curated R reader for the Civilytics US Census of Governments finance corpus —
every dollar that US state, county, municipal and township governments reported
raising and spending, from **FY1967 to FY2024**, in one queryable place.
The Census of Governments is the only nationwide source for local government
finance, and it is hard to use: item codes change meaning across vintages,
government identifiers were renumbered in 2017, and an absent value means
"published zero" in one era and "not reported" in the next. This package
handles each of those problems, and it tells you when it has — every result
carries provenance describing what was converted, what was aggregated, and
which known series breaks intersect your query.
**Scope:** government types 0–3 (state, county, municipality, township).
56 fiscal years, 46,148,034 rows, ~201 MB. There is no source data for FY1968
or FY1969. Special districts (type 4) and school districts (type 5) are
excluded pending validation.
## Where the data comes from
The corpus is published and documented at the **[US Census of Governments
Finance API](https://pages.civilytics.org/cog-api/)**. Start there for how the
data was built, how the identifier and item-code reconciliation works, and what
the corpus does and does not cover.
- **[API documentation and walkthroughs](https://pages.civilytics.org/cog-api/)**
— reference, data dictionary, and worked examples such as the
[Southern states guide](https://pages.civilytics.org/cog-api/cog-api-south-guide.html)
- **[Live API](https://cog-api.civilytics.org/api/v1/)** — the same corpus over
HTTP, for Tableau, Python, or anything that isn't R
- **[Bulk corpus on Hugging Face](https://huggingface.co/datasets/civilytics/us-cog-finance)**
— CC-BY-4.0; the same parquet files this package reads
- **[Census Bureau source data](https://www.census.gov/programs-surveys/gov-finances.html)**
— the underlying public files
## Install
```r
install.packages("uscogdata",
repos = c("https://civilytics.r-universe.dev",
"https://cloud.r-project.org"))
```
Or from source:
```r
pak::pkg_install("git::https://gitea.civilytics.org/Civilytics/uscogdata.git")
```
## Quickstart
No configuration, no credentials, no download. The package reads the published
corpus over HTTPS by default.
```r
library(uscogdata)
# Resolve a place name to a canonical government id
madison <- cog_gov_search(name = "Madison", state = "WI", type = 2)
madison$canonical_govid
#> [1] "552025209777"
# Police spending, inflation-adjusted and per capita
spend <- cog_spending(
madison$canonical_govid,
years = 2012:2022,
category = "Police",
per_capita = TRUE,
adjust_to_year = 2023
)
# What did that result do to the numbers, and what should you know about them?
cog_explain(spend)
```
`years` is required — there is no implicit full-history default.
## Two ways to read the corpus
| | Remote (default) | Mirrored |
|---|---|---|
| Setup | none | `cog_mirror(dest)`, ~201 MB once |
| Disk used | **0 MB** — HTTP range requests only | ~201 MB |
| Opening a session | ~7.5 s | ~0.1 s |
| One government, one year | ~4 s | ~0.05 s |
| One government, full history | ~7 s | ~0.1 s |
| Later queries, same session | ~1.5 s | ~0.05 s |
| Good for | trying it out, teaching, one-off questions | repeated analysis, offline work, reproducibility |
**A local mirror is roughly 60–80x faster, and it is one function call.** That is
by far the largest difference any of these settings makes. If you are going to
ask more than a handful of questions, mirror first.
Measured 2026-08-10 on a 16-core Linux workstation against the published corpus
(schema v7, `pipeline_commit 3d28ddd`), fresh R session per arm. A one-off
question costs about **12 seconds end to end remotely and 0.15 seconds
mirrored**, session setup included.
Two things the per-query rows hide:
- **Opening the session is the single largest remote cost** — larger than any
one query. It fetches the manifest and registers 23 SQL views over HTTPS, and
it lands on your first query, not on `library(uscogdata)`.
- **The cost is network round-trips, not scanning.** A repeat query against
partitions this session has already touched is ~1.5 s rather than ~4 s, and a
full-history query costs ~7 s whether it runs first or last. What you are
paying for is reaching each of the 56 yearly files over HTTPS the first time.
Nothing is written to disk in remote mode: DuckDB fetches the parquet footer,
works out which row groups it needs, and reads only those. Nothing is cached
between sessions either, so every query goes back to the network — and a session
that issues many remote queries in quick succession can be rate-limited by the
host (`HTTP Error: ... 429`). Both are further reasons to mirror for real work.
The default points at a public HuggingFace mirror of the corpus. If you would
rather not depend on a third party — for reproducibility, for an air-gapped
environment, or on principle — **the escape hatch is one function call**:
```r
cog_mirror("~/cog-corpus")
Sys.setenv(USCOGDATA_URL = "~/cog-corpus/")
```
After that, nothing in your analysis touches an external service.
### Configuration
- `USCOGDATA_URL` — corpus root: an HTTPS URL or a local path, **trailing slash required**
- `USCOGDATA_CACHE_DIR` — where the manifest is cached (default: user cache dir)
- `USCOGDATA_MANIFEST_TTL_SECS` — manifest re-fetch interval (default 3600)
- `USCOGDATA_DUCKDB_THREADS` — cap DuckDB's thread count (default: every visible core)
- `USCOGDATA_DUCKDB_MEMORY_LIMIT` — cap DuckDB's memory, e.g. `"4GB"` (default: DuckDB's own)
Each also has an `options()` spelling — `uscogdata.url`, `uscogdata.duckdb_threads`,
and so on — and the environment variable wins where both are set.
The two DuckDB caps exist for **servers**, not laptops. Unset, DuckDB claims every
core it can see, which is right for one interactive session on your own machine and
wrong when several readers share a box: each claims the whole machine and they fight.
Capping costs roughly 5% on a single query and is worth it anywhere the process is
sharing hardware.
## Amounts are in full US dollars
Every amount column this package returns — `amt_nominal`, `amt_real`,
`amt_per_capita_nominal`, `amt_per_capita_real` — is in **full US dollars**.
The raw Census source files report **thousands of dollars**, and the corpus's
own `amt` column preserves that. The verbs multiply by 1000 on the way out, so
you never have to. The conversion is recorded in every result:
```r
attr(spend, "provenance")$transformations$units_conversion
#> $applied TRUE
#> $source_unit "$1,000s (raw Census)"
#> $target_unit "$USD"
#> $multiplier 1000
```
**Do not multiply again.** If you have read elsewhere that COG amounts are in
`$1,000s` — which is true of the raw Census files and of the corpus's own `amt`
column — that rule does not apply to anything a `cog_*()` verb hands you.
Applying it twice overstates every figure by 1000x, and the result looks
plausible rather than obviously wrong.
## Concepts worth understanding before you publish a number
### Primary vs Direct vs Total spending
`cog_spending(..., expenditure_concept = c("primary", "direct", "total"))`
controls *whose* spending a result counts. Concepts are defined as sets of the
crosswalk's `spend_subtype` values, never item-code first letters — the letter
`Y` alone spans revenue, expenditure and balance codes.
- **`"primary"`** (default) — the government's own service provision: current
operations, capital outlay, assistance payments.
- **`"direct"`** — Census's published Direct Expenditure: `primary` plus
interest on debt and insurance trust benefits (e.g. pensions).
- **`"total"`** — adds the intergovernmental leg, money handed to other
governments to spend. Meaningful for one government's own budget over time,
but it double-counts when summed across governments: a state's payment to a
county is the same dollar the county reports as its own direct spending.
**Rule of thumb: any figure spanning more than one government uses `primary`
or `direct`.** `cog_geographic_rollup()` and `cog_peer_compare()` enforce that
by refusing `"total"` outright. Worked examples in
`vignette("total-spending", package = "uscogdata")`.
### General vs Total revenue
`cog_revenue(..., revenue_concept = c("general", "total"))`:
- **`"general"`** (default) — Census General Revenue: own-source taxes,
charges and miscellaneous, plus federal, state and local aid.
- **`"total"`** — General plus utility revenue (`A91`–`A94`), liquor store
revenue (`A90`), and insurance trust revenue.
Census defines these by its own identity:
```
Total Revenue = General + Utility + Liquor Store + Insurance Trust
```
Two things to know before switching to `"total"`. **Utility revenue is large
for cities** — measured on the bundled fixture, utility plus liquor store is
15.9% of city revenue, against 1.2% for states and 1.7% for counties. And the
**employee-retirement (`X`) codes stop at FY2016**, when those systems moved to
the separate Annual Survey of Public Pensions, so a `"total"` series steps down
at the FY2016/FY2017 boundary for reasons of collection scope, not revenue
(series breaks `SB197`–`SB209`).
### Reporting coverage: the Census is only sometimes a census
**The Census of Governments is a complete enumeration only in years ending in
2 and 7.** Every other year is a sample, and the sample varies enormously —
measured on the bundled fixture, Wisconsin's 608-city universe rolls up 597
governments in FY2012 and 112 in FY2019.
A statewide total resting on a fifth of the universe looks exactly like one
resting on all of it, so every multi-government result now says which it is:
```r
attr(rollup, "provenance")$coverage
# per-year n_units_expected, n_units_collected, n_units_reporting, is_census_year
```
`cog_geographic_rollup()`, `cog_peer_compare()` and `cog_find_peers()` take a
`coverage` argument — `"all"` (default), `"census"` (census years only), or
`"consistent"` (only units reporting in every requested year, a balanced
panel).
`n_units_reporting` is **category-conditional**: it counts governments with
rows for the *specific* category you asked for, so a government that was
surveyed and genuinely spends nothing in that category is indistinguishable
from one never surveyed — it is not a response rate on its own.
`n_units_collected` is the number that separates them: governments present in
the corpus that year for *any* category. `n_units_collected / n_units_expected`
is the true collection rate; `n_units_reporting / n_units_collected` is
category participation among collected units.
### Absent cells mean two different things
Before FY2012, an absent cell means Census published `$0`. From FY2012 on, it
means not reported. `cog_spending(..., complete = TRUE)` fills the requested
grid and labels every row with which it is, via `value_source`:
| `value_source` | meaning | `amt_nominal` |
|---|---|---|
| `reported` | the corpus carries this cell | as published |
| `census_zero` | dense-source year (≤ FY2011), absent — Census published `$0` | `0` |
| `not_reported` | sparse-source year (≥ FY2012), absent — unknown | `NA` |
That `NA` is deliberate. Filling a modern absence with `0` would invent data.
### Series breaks surface on their own
Catalogued breaks that intersect your query appear in provenance whether or not
you went looking for them — `series_break_refs` for breaks in a specific item code, and
`corpus_break_refs` for caveats about the corpus as a whole (dollar precision
across the 1976/1977 boundary, the FY2017 identifier change, the FY2012
dense→sparse representation change). `cog_explain()` prints both.
## How to cite
```r
citation("uscogdata")
```
The corpus itself is published under CC-BY-4.0. Cite it as:
> Civilytics Consulting. US Census of Governments finance corpus.
> https://huggingface.co/datasets/civilytics/us-cog-finance
## Contributing
Development happens on [Gitea](https://gitea.civilytics.org/Civilytics/uscogdata);
[GitHub](https://github.com/civilytics/uscogdata) is a mirror that accepts
issues and pull requests. See [CONTRIBUTING.md](CONTRIBUTING.md) for how a
patch gets from there to here.
## License
MIT © Civilytics Consulting LLC. See [LICENSE.md](LICENSE.md).