For the record, I've been a C# developer for 12 years. A Clojure dev for about ~6 months. Also, productivity is not subjective.

It is unless you're measuring the differences with an apples to apples comparison. Examples of how it was done in case studies or empirical research on software development:

1. Features developed by teams with different languages.

2. Features per day per team.

3. Lines of code that took.

4. Defect rate found after all testing and review.

5. Time taken to modify N lines of existing code.

6. Defects introduced during modifications.

7. Overall productivity rate at end of project for each that factors in initial lines of code minus what was reworked to get real lines of correct code produced averaged across each day usually.

Clojure vs Typed Racket vs commercial Smalltalk vs Ocaml or Haskell w/ meta-programming might tell use something objectively. Right now, you have no measurements on typed alternatives similar to your current tool. Your claim that it's more productive is highly subjective albeit I'll give you that prior measurements with small, sample size confirmed strongly-typed, dynamic languages give major productivity boost over statically-typed 3GL's. LISP and Smalltalk winning in that area over predecessors to C#. Your language vs similar ones remains worth measuring, though.

To be fair, C# is not the pinnacle of statically typed languages. Go is quite a lot nicer from a productivity perspective, and but there is also Haskell and OCaml if you want a more expressive type system.