https://sites.google.com/site/wdcraighead/grad-school-advice
"Preparing: Math. The most important thing in admissions is your math background (more than economics itself – I suspect most econ PhD programs would love physics and engineering majors). You should definitely have multivariable calculus and linear algebra. Statistics (that is, real statistics from the math department), real analysis and differential equations help too. You’re not really going to use all of it – though it really befuddles you at first, you’ll eventually realize that a large part of the math in economics involves taking a derivative, setting it equal to zero and doing a bunch of algebra. Nonetheless, a strong math background – not just the classes, but good grades in them – is vitally important as a signaling device to convince programs that you’ll be able to handle the rigors of the first year."
