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How the numbers are checked

Every published figure on FinanceLearn is recomputed by a second program that does not import the site engine. If the two methods disagree, or if a correctly computed figure was typed into the prose wrongly, the site does not build.

Who writes it

Jude Wallis writes and builds the pages. The same person writes EconLearn, StatsLearn, CalcLearn and PhysicsLearn. The author page is the identity. This page is the method.

The pipeline

  1. Author. The page states the identity in words and in symbols, then works a real example. Calculator defaults are that first example, so the number a reader lands on is one the build has already checked.
  2. Adversarial accuracy review. A separate pass recomputes every published figure from the stated inputs. Finance is full of arithmetic that looks right: compounding frequency, APR against APY, real against nominal, monthly against annual rates, and the sign convention on cash flows. A clean first pass means the review was not adversarial enough.
  3. Style and link review. No em dashes or en dashes. Meta titles stay short. Every internal link has to resolve. Currency in the data files is escaped so a dollar sign cannot be read as a maths delimiter.
  4. Assemble. A script writes one object-literal style into the published data tree. If any guard fails, it rolls back every file it wrote.
  5. Independent recomputation. scripts/check-finance-math.mjs does not import src/lib/finance.ts. It walks a loan schedule instead of using the closed payment formula, and it compounds period by period instead of using a power. Agreement is required, not hoped for.
  6. The figure has to appear. A number that was computed correctly and then mistyped in the prose still fails the build. The checker looks for the published figure in the words a reader sees.

What the other guards stop

TeX that would render as an error span, a dead internal link, a calculator route with no "not financial advice" notice, a sitemap whose URL count disagrees with the content on disk, a drag surface that has not declared its axis, and a page that went dynamic. The factor tables recompute every cell by a second method as well.

Scope

This is educational material, not financial advice. The calculators show what a formula produces from the inputs you give it. Statutory rates and wage bases are inputs because legislation resets them. Put the figure your stub, your course, or the issuing authority is using.

First-party citation measurements live on the research page. How-to and formula URLs under answers point at the guide or calculator that owns the identity.

If a published figure is wrong, write to Jude Wallis on LinkedIn with the page and the sentence. Corrections take priority over new pages. See also about FinanceLearn.