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Spot the Cooked Books · Chapter 8

Benford's-Law Tester

When people invent numbers, their fingerprints show up in the first digit. In big, wide-ranging real data, leading 1s appear about 30% of the time and 9s only about 5%. Fabricated figures break the staircase.

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Paste at least 30 figures (100+ works best) and press Run Benford check.
From the book — Chapter 8. Benford's expected shares: 1 ≈ 30.1%, 2 ≈ 17.6%, 3 ≈ 12.5%, 4 ≈ 9.7%, 5 ≈ 7.9%, 6 ≈ 6.7%, 7 ≈ 5.8%, 8 ≈ 5.1%, 9 ≈ 4.6%. The Tell: fabricated numbers over-use middle digits (4, 5, 6) and spike just under approval limits. Only works on big, wide-ranging data (invoices, expenses, transaction ledgers) — not on tightly-bounded numbers (heights, ZIP codes, prices under $10).

A broken staircase is a reason to look closer — trace the spike, ask who prepared the figures, and compare two periods. An odd distribution is a question, not a verdict. Everything stays in your browser — no sign-up, nothing stored.