Frequently, companies will specify in job adverts that a potential candidate must have an arbitrary number of years' experience. Such requirements amuse me, as the experience metric is flawed. For me, it shows a lack of understanding and a lack of thought. For the purposes of analogy, take football as an example. After an arbitrary five years, a player at a Premier League club is is going to have far greater experience in real terms than someone playing in League 2. To use experience on its own is baseless and simply prevents the recruiting company from having a chance at finding the best people.
Within development, there are numerous factors which contribute to how much qualitative experience an employee can gain.
These include the type of projects worked on: is the work maintaining a legacy platform, wrestling it into a more maintainable structure? Is the bulk of the work new, short lived projects utilising a particular framework? How many different technologies is the developer exposed to as a result of the nature of the projects?
Repetition, or lack thereof, also plays its part. If you're doing the same thing every week for five years, for each year spent you aren't gaining much at all, versus someone else who's had a much wider range of challenges within a shorter space of time.
The type of problems faced by the team play a major part. This relates to the nature of the products worked on. A large application that has had high growth will create different challenges for the developers working on it than they would have otherwise had to face in their careers. Challenges due to sheer scale. Challenges you won't have to face if you've been plodding along in League 2.
The team and management are also very important. Not only does there need to be a high level of technical competence amongst your co-workers, but there needs to be a willingness to knowledge share. Ideas, code reviews, implementation and adaptation of best practices. Management needs to provide the leeway for developers to explore new ideas and new methodologies, and be willing to adapt and implement new processes as required. Continuous improvement applies not only to product development but to personal development as well.
If tasked with recruiting, and presented with two candidates, one of whom has two years' experience and one of whom has five, I posit that the decision facing the recruiter is not as straightforward as it may seem, and that the companies specifying such a metric in their job descriptions are being short-sighted and nothing short of foolish. It is not, as it may seem, an easy way of filtering applications to produce a shortlist.