Also look at the Economics' Department Website Advising FAQ
Students interested in the economics major should take Economics 101 as first-years, and if desired, one or two economics classes numbered below 240. They should also take Math 110 or Math 101 (or a higher math class) as first-years if possible, since calculus is a prerequisite for two of the sophomore economics core classes (Economics 241 and 242). Students who take Math 100 must take it no later than fall term sophomore year in order to complete the economics major on time.
Majors normally take the core classes (241, 242, and 243) as sophomores. Majors may only take courses numbered below 240 as first-years or sophomores. Students interested in ID majors with economics as one half should complete the economics core no later than the middle of the junior year.