International PPP for faculty salaries
Not exactly what I would have thought:
Canada comes out on top for those newly entering the academic profession, average salaries among all professors and those at the senior levels. In terms of average faculty salaries based on purchasing power, the United States ranks fifth, behind not only its northern neighbor, but also Italy, South Africa and India.
You will note however that this is not covering the extreme right hand tail of top faculty salaries in top U.S. universities, but rather a measured mean from public institutions. There is more here, hat tip goes to Jacob Levy. In percentage terms, the biggest gap between entry salaries and top salaries is found in China. There is much more data here.