Planned changes to the curricula of two economics courses will begin to affect students in the fall.

Economics 51, currently a principles of macroeconomics course, will also incorporate principles of microeconomics.

The new Economics 55 course, which will not officially be implemented until Spring 2007, will be more math-intensive, with a Math 31/32 prerequisite. Students taking Economics 51 this semester will take the existing Economics 55 course in the fall.

In response to the new economics curricula, prerequisites for the public policy studies major have changed. In the fall, PPS students will be able to take either Economics 51 or 55 to satisfy their economics prerequisite. Currently, students must take Economics 55, for which 51 or an equivalent course is a prerequisite.

Emma Rasiel, director of undergraduate studies for the Department of Economics, said changes to the curriculum were necessary because the department currently lacks a true principles of microeconomics course. "Our principles course is solely macroeconomics, and instead of a principles of microeconomics, we have two intermediate micro classes," Rasiel said. "One is with calculus, and one without."

She added that the current system is inefficient for many PPS majors.

"These students are taking more macroeconomics than they probably need for their major," Rasiel said. "I'm an economist, so I'd never say it's a bad thing, but in the context of their major, it's not necessary."

Rasiel said the economics department made changes with the intention of better serving both economics and non-economics majors. "It's a benefit to public policy students because they need some micro as well as macro, and they will now get it all in one course," she said.

Rasiel added that officials in the Nicholas School of the Environment and Earth Sciences prefer their students to learn microeconomics and said that the new Economics 51 course will fulfill the need in one semester.

The effects of the course changes on PPS requirements extend beyond the economics prerequisites. Currently, PPS majors take either Public Policy 128, called "Microeconomic Policy Tools," or an approved substitute for the course taught by an economist within the public policy department, said James Hamilton, professor in the Department of Public Policy Studies.

Under the new system, only students who take Economics 55 will have the option of taking a substitute course, while those who take Economics 51 will be required take PPS 128.

Hamilton said the department expects enrollment in PPS 128 to increase significantly. Although approximately half of all PPS majors opt to take PPS 128 instead of a substitute under the current rules, Hamilton anticipates that after the change the proportion will rise to 90 percent. The class, now offered only in the fall, will become available for both semesters to accommodate increased enrollment.

"This change allows students to do what we've always hoped they would do," Hamilton said. "We want them to think like economists and then apply it to policy."

Hamilton added that he expects the new Economics 55 course to be primarily the choice of economics and PPS double majors, who number about 20 students each year.