Given the recent post questioning the value of the MBA degree, one would think the Economist powers-that-be would not be staffing up MBAs. But then, if not useless MBAs, how would the Economist explain this chart they printed next to the said article?
More likely, the red part is the incremental salary, possibly explained by the value of the degree while the gray part is the pre-MBA salary.
However, since the author has few nice words to say about business schools, one can never be 100% sure if he is presenting some counter-intuitive data.
In the Trifecta checkup, one would find nothing wrong with the chart type, nor is there anything wrong with asking the return on investment of an MBA degree.
The third component -- having the right data -- is what renders this effort a failure. It is too simplistic to measure return on investment on the salary upon graduation. Surely, one must also include future career paths, intangible benefits from network relationships, personal development, etc.