Benford's Law can detect accounting fraud

In naturally occurring datasets — populations, river lengths, financial transactions — the first digit is '1' roughly 30% of the time, '2' about 18%, and higher digits progressively less frequently. This counterintuitive pattern, called Benford's Law, was noticed by physicist Frank Benford in 1938. When people fabricate numbers, they tend to distribute first digits more evenly, violating Benford's Law. Tax authorities and forensic accountants now use Benford's Law analysis as a first-pass fraud-detection tool, and it has been admitted as evidence in US federal courts.

Source: Nigrini, Benford's Law: Applications for Forensic Accounting, Auditing, and Fraud Detection (2012)