From Diversifying Economic Quality: A Wiki for Instructors and Departments
Musicians often times perform a variety of tasks in one sitting such as performing scales, sight-reading, and performing pieces. Athletes also execute a variety of tasks in order to master a sport such as performing drills for speed, strength, and agility. Why shouldn't students do the same? Studies have demonstrated that by studying a variety of material in a single session (such as completing mixed problem sets, or alternating between reading passages and completing short answer questions) improves information retention.
Suggestion: Be sure to alternate between different assignments while studying. For economics, repeatedly draw graphs for a period of time, then read the text, and finally complete a problem set.