Can we compare local, foreign worker output?

With foreign workers, making up about one-third of our current workforce, the question that has inevitably been raised is how well they are performing in relation to Singaporeans. Economics assistant professor Davin Chor said, "Ideally, we would want to compare apples with apples and ask ourselves, how does the output generated by a foreign worker in a given firm compare with the output that would be generated had a local worker been employed instead to do the same work?"