In 2009, researchers audited 25 operational spreadsheets across five organizations. One workbook at a large firm contained a cell wrong by $110,543,305, a 137.5% distortion. Built within the previous year and in active use, the error had survived normal operations undetected.
What struck the researchers wasn't the scale of the mistake. It was the culture around it. Most spreadsheet developers did no formal testing. Several acknowledged that certain formulas "weren't quite right" but accepted outputs that looked reasonable. Models had been inherited from predecessors or grown organically, accumulating logic nobody fully owned.
This is a thirty-year echo of a specific organizational choice. When VisiCalc arrived in 1979, it let business users encode decisions without waiting for programmers. Organizations gained speed. What they never built were the review structures that programmers would have brought with them. Independent formula audit is straightforward. In most organizations, it has always been nobody's job.
Study: Powell, Baker, Lawson (2009) — 25 operational spreadsheets, 5 organizations, independently audited
Errors found: 117 confirmed; 70 with quantitative impact; 7 exceeding $10M
Testing practices: "Very few used any formal approach; most did no testing at all"
Developer awareness: Several knew formulas were wrong but saw outputs as acceptable
Complexity vs. controls: Tax-liability models at a major financial firm — calculating billions in obligations — were "astonishingly complex, difficult to understand, and error-prone"
Inheritance problem: Developers cited organic growth and inherited designs as primary reasons for poor structure
One counterexample: A small firm produced five error-free spreadsheets, described as "thoughtfully designed, well documented, easy to understand"
Applicable standard: Independent formula review — described in PCAOB auditing guidance, rarely implemented outside formal audits