The terms on this site, explained

The CFR

The Code of Federal Regulations is the official rulebook of the United States federal government — every general and permanent rule its agencies have issued, organised into 50 numbered titles by subject (Title 21 is food and drugs, Title 40 is the environment, and so on). Laws passed by Congress say what must happen; the CFR is where agencies spell out how.

The eCFR

The electronic CFR is the continuously updated online edition of the CFR, published by the Office of the Federal Register and the Government Publishing Office. It is updated within days of rule changes — and it is the source this site measures. Note that the eCFR itself is an editorial compilation, not the legally authoritative edition; see about & attribution.

Titles, chapters, parts, sections

The rulebook nests like a book: a title covers a broad subject, a chapter within it usually belongs to one agency, a part covers one program or topic, and a section is the individual rule you cite — “40 CFR 60.290” means title 40, part 60, section 60.290.

Total regulation

An agency's total regulation is every rule it manages, measured in words. Where a rule is managed jointly with another agency, it counts in full here — if two agencies are each fully responsible for a rule, each one's total should reflect that. Because of this, adding every agency's total together counts jointly managed rules more than once; use shares for sums.

Share of all regulation

An agency's share is its slice of the whole rulebook: jointly managed rules are split evenly between the agencies in charge, so every word lands in exactly one agency's share and shares can be fairly compared or added. When an agency manages nothing jointly, its share and its total are the same number.

Total federal regulation

The size of the whole rulebook in words, counting every rule once. This is the site's headline number, and the honest answer to “how much federal regulation is there?”

Counting shared rules once per agency

The alternative corpus figure: the same rulebook, but a rule managed by several agencies is counted once for each of them. It answers “how much regulation are agencies responsible for, in total?” — a responsibility measure, not a size measure, which is why it runs slightly higher than the total above.

Shared rules (joint management)

Some rules have more than one agency in charge — the EPA and the Department of Justice share one chapter of environmental rules, for example. The eCFR names every agency for each of these. See every jointly managed area →

Areas managed (scopes)

The eCFR assigns each agency named slices of the rulebook — a whole title, a chapter, or a single part. This site calls them areas (the data calls them scopes). An agency's numbers are built by measuring each of its areas.

Coverage

How many of an agency's areas could actually be measured in the current build. When even one area cannot be measured, the agency's totals are reported as unmeasured rather than as a partial sum — a partial sum looks exactly like a real number, and this site never publishes one.

Word counts

Every count is produced by parsing the eCFR's own XML and counting the words of actual regulation text — headings, authority notes, source citations and tables of contents are excluded (measured at 18.4% of the text in a sample chapter). Nothing is estimated from file sizes. The full rules are on the methodology page.

Reserved

A slot the rulebook keeps but that contains no rules — a placeholder for future use or the site of a repealed rule. Reserved items show a word count of zero, which is a measured fact, not a missing value.

“Not measured” and the em dash (—)

When a value could not be measured, this site shows an em dash with the reason — never a zero, and never a guess. Every unmeasured value in the build is listed on the data quality page.

Amendments

A change to a rule, published by the issuing agency. The amendment charts count sections changed per month, dated by the day the change was published in the eCFR.