I often heard the claim that dynamically typed languages are more productive than statically typed languages. What are the reasons for this claim? Isn't it just tooling with modern concepts like convention over configuration, the use of functional programming, advanced programming models and use of consistent abstractions? Admittedly there is less clutter because the (for instance in Java) often redundant type declarations are not needed, but you can also omit most type declarations in statically typed languages that usw type inference, without loosing the other advantages of static typing. And all of this is available for modern statically typed languages like Scala as well.

So: what is there to say for productivity with dynamic typing that really is an advantage of the type model itself?