There are many reports of extremely high occurrence rates for bugs in spreadsheets. From reading them, you might think that very few spreadsheets are error-free.
However, many people who are aware of the likelihood of errors in spreadsheets go to great lengths to find and remove them. I have found few significant errors in the often large and complex spreadsheets I have reviewed (mainly in the insurance industry).
In my view the true significance of bugs lies not in their existence, which can lead to spreadsheets producing erroneous results, but in the enormous amount of time and effort that goes into preventing them. Spreadsheets are usually built and maintained by people who have little or no software engineering expertise. These people often:
- Do not have good software development processes
- Are not aware of the characteristics of good software and how they apply to spreadsheets
- Do not know good methods of testing and reviewing software
- Do not know how to design software (especially spreadsheets) so as to reduce the likelihood of bugs
I believe that the use of simple software engineering techniques can help. Some of these techniques are described, somewhat briefly, in other notes on this site.
The following external links are relevant: