I wouldn't be surprised if it is actually faster to develop in statically typed languages once projects reach a certain size. It makes refactoring so much easier, and it's a lot easier to reason about what a functions arguments could be. I've had cases before where the easiest way to tell what a function accepted as an argument was to just run the program and print out the input. If it was statically typed, I know exactly what the arguments are, and can easily see the effects of modifying one of those arguments. With dynamic typing, I spend a lot of time just looking at how a function is used elsewhere in the code to make sure I don't break anything.