Why spreadsheets suck at modeling

Every time I step onto an airplane I shiver at the thought that the engineers who designed it might have used Excel (or any other spreadsheeting tool for what matters) for their calculations.
It’s time for a good rant against spreadsheets, after having looked at all sort of mistakes made by engineers and finance specialists while modeling anything from a boiling mixture to the the cash flow for a project financing.

The modeling work typically starts with paper and pencil, then at some point a pocket calculator is picked up and finally someone sits in front of a computer and fires up her favorite spreadsheeting program. BTW, my favorite spreadsheeting program is quantrix, a multi-dimensional spreadsheet.

The apparent simplicity of the spreadsheet metaphor drags the user into the illusion of unlimited flexibility, immediate and transparent results and zero pain.

In reality there are several fundamental weaknesses in using spreadsheets which invariably result in very high costs in the quality control and maintenance:

The bottom line is: never use a spreadsheet for your models, if they are supposed to live more than a month or if they will end up in other people’s hands.