First, some criteria:
- The product is an application and is heavy on user interaction. Think web 2.0 or mobile application, not a marketing or commerce site, or some back-end tool with only command-line access.
- I realize that it is not always clear who is a UX person and who is a developer (nor should it be), so I'd like to focus on overall team resource allocation. For instance, "My team puts 25% of our resource-time into UX design/research vs. 75% of our resource-time in development."
- I am not distinguishing between front-end and back-end development as it is too platform-specific and difficult to tease out the dividing like. It's all software development for this question.
- EDIT: Development is occurring in an agile-esque, ongoing manner, rather than a one-time, big-bang delivery.
- How does this proportion commonly look in practice?
- How should it look? Or, better yet, what has been the proportion on successful teams?
(I realize this is a classic "it depends" question, but I suspect that there is some use in asking when constrained by a few parameters, and allowing that conditions will vary. I am also open to suggestions to further constrain the question.)