IS/LM curves, how confusing

I use the following simpler method:

When the real yield curve is smooth we are classical and moving smoothly about equilibrium.. When the yield curve has jaggedness then we have inventory shortages and gluts with opportunities for stimulus.

Closely aligned is the concept of minimum phase, where phase is the alignment between inventory supply flows and demand flows. Linear estimation theory tells us that we are not minimum phase if the yield curve is jagged. An inverted yield cure is one where inventory flows, in the aggregate, have negative feedback.

Linear estimation theory applies because economies are built on the expectation operator.