Advice on Mathematical Preparation
Although economics graduate programs have varying admissions requirements, graduate training in economics is highly mathematical. According to Lee Hansen's (1991) report, "The Education and Training of Economics Doctorates: Major Findings of the American Economic Association's Commission on Graduate Education in Economics," when presented with the following five levels of mathematics
 high school mathematics only
 basic calculus and linear algebra
 applied mathematics, differential equations, linear programming, and basic probability theory
 advanced calculus, advanced algebra and stochastic processes
 real and complex analysis, advanced probability theory, and topology,
economics Ph.D. students at the time reported that the level of mathematics used in their various graduate courses was slightly above level 3 ( p.22). There has been an upward trend in the level of mathematics used in graduate courses since that time. For example, the econphd.net website suggests that:
"Two or three terms of calculus, and often linear algebra, are deemed minimum preparation; similarly a semester of mathematical statistics. Firstyear graduate courses draw heavily on real analysis. Background in real analysis is highly valued and indeed almost expected of a strong applicant. Real analysis is usually the first "rigorous" mathematics course, where you have to work through all proofs and write some yourself. The course is supremely effective preparation for initial graduate courses."
 The CalStateEast Bay Economics Department has a page describing its recommendations for Mathematics Preparation for a Ph.D. in Economics http://www20.csueastbay.edu/ecat/graduatechapters/gecon.html

Harvard Professor Greg Mankiw has a blog on Why Aspiring Economists Need Math
http://gregmankiw.blogspot.com/2006/09/whyaspiringeconomistsneedmath.html
 Duke University provides a recommended PhD preparation track of courses that includes advanced mathematics, econometrics, and statistics. http://econ.duke.edu/mastersprogram/requirements/areasofconcentration/phdpreperationtrack

The University of Wisconsin has description about its Departments expectations for math preparation
http://www.econ.wisc.edu/grad/math_reqs.html