She took a lot of heat for saying it, but I agree with Talking Barbie: math class is hard. It's especially hard in economics. And I find it much harder than most economists. So I have always been on the hunt for devious little tricks to avoid doing hard math. Here's one such trick:
Think back to the very simple Keynesian Cross model. There were two types of math problems the students are forced to do:
Type 1. Assume G=100. Solve for Y.
Type 2. Assume full-employment Y=200. Solve for G that gets us to full employment Y.
Most of the time, economists solve Type 1 problems. And when they have the solution, they use that solution to see whether an increase in G would increase or decrease Y.
But what policymakers really want is the solution to Type 2 problems. For example, a central bank targeting 2% inflation faces a Type 2 problem.
Sometimes there are two Y's for one G, and solving the Type 1 problem should let you see that. But other times there are two G's for one Y, and solving the Type 2 problem should let you see that. That problem cuts both ways.
In the simple Keynesian Cross model, Type 1 and Type 2 problems are equally hard to solve. But when we introduce expectations and intertemporal optimisation into the model, Type 1 problems can be much harder to solve than Type 2 problems.
So pose the question as a Type 2 problem:
"Assume inflation is always at 2% and output is always at potential. So agents always expect 2% inflation and always expect output to be at potential. Solve for the monetary and/or fiscal policies that would make that happen."
That's much easier than the Type 1 version.
That's the devious little trick I used in this post on fiscal policy in New Keynesian models to skive off doing the (for me) impossibly hard math of a Type 1 problem. The solution to the Type 2 problem popped out very easily. And it taught me something the much cleverer economists solving Type 1 problems seem to have missed.