The yield spread since the end of the Great Recession

Looking at the yield spread since June 2009, an optimist might see this:

Graph #1: Excel Polynomial Order 5 Trendline

A pessimist might see this:

Graph #2: Excel Polynomial Order 2 Trendline

A panicking pessimist:

Graph #3: Excel Polynomial Order 3 Trendline

And a realist:

Graph #4: Excel Polynomial Order 6 Trendline

What do you see?