"not bad but not that impressive either". I think the 75% is accurate, but even at 50% it's impressive. The number of lines of code in an application makes a big difference to understanding the code and maintaining it. Erlang is just a much more modern language which benefits from having idioms which simply don't exist in c++. Another big win is erlang's message passing model which is much easier to grok and far less bug prone than threads.