the problem with study like airbnb is that while tooling would have caught X% of bugs of type A, it in no way means those wouldn't just be replaced by bugs of t

the problem with study like airbnb is that while tooling would have caught X% of bugs of type A, it in no way means those wouldn't just be replaced by bugs of type B. bugs are (in part) function of code and tooling complexity, making some bugs harder to introduce doesn't reduce that complexity. risk compensation principle is another factor, and so on. i haven't yet seen strong evidence that static typing really reduces bug density.