You may believe that, but the fact is that we haven't been able to find any evidence to support the fact that "new types" significantly increase correctness and have a greater return on investment, either compared to "old types" or in general, and not for lack of trying. At this point, it's okay to believe it, but I'd be very careful about being so sure about it. Large effects are very easy to detect and are hard to hide. The fact that we haven't been able to easily see the effect in any rigorous way, suggests that even if there is some positive effect, the most reasonable assumption we can make right now is that it is most likely small. Having had experience with both "new types" and "old types," my personal impression (which is certainly not rigorous or necessarily trustworthy) is that such claims about a big bottom-line impact are exaggerated. Sometimes people feel they're writing more correct programs more easily, but the bottom line doesn't quite support it.