If documentation is how you get your data and code correct, than sure, it is important. But that's a methodology, a mean to an end. There are other methodologie

If documentation is how you get your data and code correct, than sure, it is important. But that's a methodology, a mean to an end. There are other methodologies that are not based on documentation, most notably, Agile. But let's imagine. You use your documentation-centric methodology, and produce software, with good data structures, algorithms, and documentation. Problem is, your server room is on fire and so are all your backups, you can still recover some data but it may fail at any time, what will you try to recover first? I don't know about you, but for me, it definitely won't be the documentation (unless they are legal documents, maybe). If I lose the data and code, I will be left with nothing workable, I will have to do everything all over again, not from scratch because of the good documentation, but in the meantime nothing. If I lose only the documentation, future teams will have a hard time reverse engineering the code and all that, but in the meantime, they will still have a working product, and will still be able to do minor evolutions and bug fixes without too much trouble. That's what I mean when I am saying that documentation is the least important. It means the least important as a product, it does not mean it is the least important to your methodology, or that you should not write it first, especially if you use it as a working document to make sure you get the other parts right.