The fault is not in Excel, which is an excellent piece of software. All the problems identified are the fault of poor math.
After the London Whale trade blew up, the Model Review Group discovered that the model had not been automated and found several other errors. Most spectacularly,
“After subtracting the old rate from the new rate, the spreadsheet divided by their sum instead of their average, as the modeler had intended. This error likely had the effect of muting volatility by a factor of two and of lowering the VaR . . .”
It's not like programmers are immune from making such errors. You can put the wrong equation into a page of C or Java as you can onto an Excel spreadsheet.
> It's not like programmers are immune from making such errors. You can put the wrong equation into a page of C or Java as you can onto an Excel spreadsheet.
The difference is that programmers know they will make such errors and thus have developed tools, techniques and a culture that acknowledges the necessity for testing to find and eliminate bugs.
In contrast, I'd wager that less than 0.01% of financial Excel sheets has automated tests, and less than 0.1% has a written test plan. If you confront your typical "work-hard-party-hard" hotshot trader with demands for such, the response is most likely "Testing? I wrote it, I know it works, do you think I'm stupid?"