Seems to me that it's economics. Theoretic physics seldom goes beyond vector calculus, special functions, ODE/PDE, and basic group theory. While in economics, many fields incorporate math tools that are far more intellectual demanding. E.g. in asset pricing and econometrics, measure theory and SDE are used quite intensively; in structural micro and macro, sophisticated computational tools from applied math and statistics are used everywhere; etc.
Good if agree.