There were a few studies on ada (avionics software) and productivity when the language first came out, and ada scored very well compared to the state of the art

There were a few studies on ada (avionics software) and productivity when the language first came out, and ada scored very well compared to the state of the art at that time. People learned that using static typing and sub-typing moved a lot of defects from runtime to compile time. (that was sure my experience; getting it to compile took hours, but runtime errors were greatly diminished). Looking back, the power of the "spec and body", IN and OUT parameters, and such where just so much more powerful than Fortran or Assembly or even JOVIAL. C was too uncontrolled and wild.