Methodology

Tax expenditure costs come from the Joint Committee on Taxation’s annual estimates, with Treasury figures used where JCT does not publish a comparable line. Direct spending comes from CBO baseline projections and agency outlay reporting.

Two caveats apply throughout. First, tax expenditure estimates are not additive: repealing two provisions rarely raises the sum of their individual scores, because taxpayer behaviour and interaction effects change. The combined figure on the homepage is a scale indicator, not a revenue estimate. Second, some provisions defer tax rather than forgive it, and cash-flow estimates overstate their long-run cost relative to present-value measures. Where that applies, the detail page says so.

One entry does not sit on the same basis as the rest. Carried interest is not scored as a separate tax expenditure by JCT, so its figure is CBO’s estimate of the revenue raised by taxing it as ordinary income, which is a repeal-side revenue estimate rather than a revenue-forgone calculation. The two are not the same quantity and should not be read as interchangeable. It is included because the provision is structurally central to what this site tracks, and its cost note says plainly which measure it uses and for which year.

A 0–100 score where 0 means the benefit is spread across taxpayers roughly in proportion to their number, and 100 means it is captured by a narrow, structurally identifiable class. It is built from distributional tables where those exist, and from the statutory eligibility structure where they do not.

It is a judgement, not a measurement, and the interface is built to keep it honest about that: the score renders as a marker on a track rather than as a chart, and the reasoning behind it appears next to it everywhere it is shown. A Lorenz curve would imply a precision the underlying evidence does not support.

Where possible the score reflects asset position, entity form and form of return rather than income percentile, because that is what the statutes actually key on. A provision that rewards holding appreciated assets is not well described by an income decile.

Writing c for the concentration score as a fraction:

• Total cost
  Annual taxpayer cost, largest first.
  sort by: cost
• Most cost, least good
  Annual cost multiplied by the concentration score, the dollars flowing to a narrow structural class.
  sort by: cost × c
• Most narrowly captured
  Concentration score alone, ignoring size. This is the softest of the four views: it drops the cost figure, which is verified, and ranks on the concentration score, which is a judgement. Rows whose score is grounded in a published distribution are marked.
  sort by: c
• Most good, least cost
  Annual cost multiplied by how broadly the benefit spreads, shown for contrast, not as criticism.
  sort by: cost × (1 − c)

The second and third measures sum back to total cost, which is a deliberate constraint: a transfer cannot score badly on both without being large in the first place, and a large, broadly-distributed transfer will rank near the top of the third view rather than disappearing. That is the check on the tool measuring its own selection criteria.

The fourth is different in kind and should be read with more caution than the others. It drops the cost figure entirely, and the cost figure is the verified half of the pair. What remains is the concentration score on its own, so the ranking is a ranking of judgements. Only a minority of scores are currently anchored to a published distribution, and that view marks which ones those are on every row. It answers a narrow question, which provisions are written for the smallest group, and it deliberately does not answer whether the money is well spent, because nothing on this site measures the public benefit a provision produces.

Freshness is computed from each source document’s publication date at render time rather than stored as a field, so it cannot silently go out of date. Thresholds are deliberately generous because the underlying documents are annual or biennial: an eighteen-month-old JCT figure is normal, not neglected. Anything over four years old is marked stale and should be read as historical context.

It covers federal transfers only, and only the largest of them. It does not name individual beneficiaries, attempt to attribute lobbying spend to specific provisions, or model second-round economic effects. Lobbying figures shown are sector aggregates covering many issues, and should be read as an indicator of organised interest rather than as a price paid for a particular line of the tax code.