The quality and reliability of spreadsheets is known to be poor.
Bishop & McDaid (2007)
Your spreadsheets may be disasters in the making.
Caulkins, Morrison, & Weidemann (2006)
Spreadsheets are easy to use and very hard to check.
Chen & Chan (2000)
60% of large companies feel 'Spreadsheet Hell' describes their reliance on spreadsheets.
Murphy (2007)
It is now widely accepted that errors in spreadsheets are both common and potentially dangerous.
Nixon & O'Hara (2010)
A significant proportion of spreadsheets have severe quality problems.
Ayalew (2007)
People tend to believe their spreadsheets are more accurate than they really are.
Caulkins, Morrison, & Weidemann (2006)
Even obvious, elementary errors in very simple, clearly documented spreadsheets are... difficult to find.
Galletta, et al (1993)
Spreadsheets are extraordinarily and unacceptably prone to error.
Dunn (2010)
Spreadsheets are dangerous to their authors and others.
Durusau & Hunting (2015)
Untested spreadsheets are riddled with errors.
Miller (2005)
Spreadsheets have a notoriously high number of faults.
Rust, et al (2006)
Spreadsheets can be viewed as a highly flexible programming environment for end users.
Abreu, et al (2015)
The results given by spreadsheets are often just wrong.
Sajaniemi (1998)
Research on spreadsheet errors is substantial, compelling, and unanimous.
Panko (2015)
Despite being staggeringly error prone, spreadsheets are a highly flexible programming environment.
Abreu, et al (2015)
Errors in spreadsheets... result in incorrect decisions being made and significant losses incurred.
Beaman, et al (2005)
Spreadsheet development must embrace extensive testing in order to be taken seriously as a profession.
Bock (2016)
...few incidents of spreadsheet errors are made public and these are usually not revealed by choice.
Kruck & Sheetz (2001)
Spreadsheets contain errors at an alarmingly high rate.
Abraham, et al (2005)
It is irrational to expect large error-free spreadsheets.
Panko (2013)
Every study, without exception, has found error rates much higher than organizations would wish to tolerate.
Panko (1999)
Spreadsheets are commonly used and commonly flawed.
Caulkins, Morrison, & Weidemann (2008)
Every study that has looked for errors has found them... in considerable abundance.
Panko & Halverson (1996)
Spreadsheet shortcomings can significantly hamper an organization's business operation.
Reschenhofer & Matthes (2015)
1% of all formulas in operational spreadsheets are in error.
Powell, Baker, & Lawson (2009)
Developing an error-free spreadsheet has been a problem since the beginning of end-user computing.
Mireault (2015)
The issue is not whether there is an error but how many errors there are and how serious they are.
Panko (2007)
Overconfidence is one of the most substantial causes of spreadsheet errors.
Sakal, et al (2015)
The software that end users are creating... is riddled with errors.
Burnett & Myers (2014)
Most executives do not really check or verify the accuracy or validity of [their] spreadsheets...
Teo & Tan (1999)
Spreadsheets are notoriously error-prone.
Cunha, et al (2011)
Programmers exhibit unwarranted confidence in the correctness of their spreadsheets.
Krishna, et al (2001)
Spreadsheets are more fault-prone than other software.
Kulesz & Ostberg (2013)
Spreadsheet errors have resulted in huge financial losses.
Abraham & Erwig (2007)
Spreadsheets... pose a greater threat to your business than almost anything you can imagine.
Howard (2005)
Despite overwhelming and unanimous evidence... companies have continued to ignore spreadsheet error risks.
Panko (2014)
Studies have shown that there is a high incidence of errors in spreadsheets.
Csernoch & Biro (2013)
Spreadsheets are often hard, if not impossible, to understand.
Mireault & Gresham (2015)
94% of the 88 spreadsheets audited in 7 studies have contained errors.
Panko (2008)
Spreadsheet errors... a great, often unrecognised, risk to corporate decision making & financial integrity.
Chadwick (2002)
The untested spreadsheet is as dangerous and untrustworthy as an untested program.
Price (2006)
Never assume a spreadsheet is right, even your own.
Raffensperger (2001)
Spreadsheet errors are pervasive, stubborn, ubiquitous and complex.
Irons (2003)
Most large spreadsheets have dozens or even hundreds of errors.
Panko & Ordway (2005)
Spreadsheet errors are still the rule rather than the exception.
Nixon & O'Hara (2010)
A lot of decisions are being made on the basis of some bad numbers.
Ross (1996)
Spreadsheets are the most popular live programming environments, but they are also notoriously fault-prone.
Hermans & van der Storm (2015)
Errors in spreadsheets are as ubiquitous as spreadsheets themselves.
Colbenz (2005)
Spreadsheets are alarmingly error-prone to write.
Paine (2001)

Spreadsheet bibliography

Title What we know about spreadsheet errors
Authors Raymond R. Panko
Year 1998
Type Article
Publication Journal of End User Computing
Series Volume 10, Number 2, Spring, pages 15-21
Abstract

Although some spreadsheets are small "scratch pad" applications, many are large and complex, and many mission-critical decisions depend on spreadsheet analyses.

In recent years, we have learned a good deal about the errors that people make when they develop spreadsheets. In general, errors seem to occur in a few percent of all cells, meaning that for large spreadsheets, the issue is how many errors there are, not whether an error exists.

These error rates, although troubling, are in line with error rates in programming and other human cognitive domains. In programming, we have learned to follow strict development disciplines to eliminate most errors. Surveys of spreadsheet developers indicate that spreadsheet creation, in contrast, is informal, and that few organizations have comprehensive policies for spreadsheet development.

Although prescriptive articles have focused on such disciplines as modularization and having assumptions sections, these may be far less important than post-development testing.

Full version Available
Also see Revised version (2008)
Sample
Probability of spreadsheet error
Probability of spreadsheet error

This equation calculates the probability that a spreadsheet contains at least one error cell (E), given n cells and probability e that each cell contains an error.

Even for a small cell error rate and a modest number of cells, a spreadsheet is highly likely to contain errors.

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