The stochastic growth model, which is the workhorse of modern economics, cannot be easily vectorized, and usually requires tight inner loops to get good performance, or rewrite the computational kernels in C. Codes such as Dynare (http://www.dynare.org) do exactly that. In my opinion, this is where Julia shines - it provides high performance in a dynamic language, much at the level of R or MATLAB. Then again, being a co-creator of Julia, I am probably biased, but this is exactly the kind of thing that motivated work on Julia in the first place.