It's a good question, and it really depends. I have one system where clojure performs better than java. It's not an apples-to-apples comparison as the java sou

It's a good question, and it really depends. I have one system where clojure performs better than java. It's not an apples-to-apples comparison as the java source is very rigid and stateful. There's a ton of recalculations being done and there's almost no way to thread it out because the current implementation relies heavily on mutation. The clojure equivalent is much smaller and just overpowers the java implementation due to the ease of threading (pmap, memoize). In that specific example I was looking at maybe 20x performance increase? I have another test where I cannot even get close to java performance. Even after adding in type specific checks. In that example java wins because it's a native/primitive java implementation. Even without threading the java side wins because it's been reduced to such a simplistic operation (500 lines of java code using only primitive types) that the overhead of clojure can't beat it. In this test java is about 5x fastar than the clojure equivalent. It really depends on what you are doing I tend to think of it like raw java > clojure > over engineered java... In some instances it can be very, very powerful.