Some may argue that the present, wider high yield spread is a function of the low Treasury yields, but historically there has been little correlation between the spread-versus-Treasuries and nominal Treasury yields.
The college spread has elevated the function of slot receivers, who often work the middle of the field as safety valves whom the quarterback can target if pressured.
But the spread between the price of the raw material and the price of the finished good is a function of the supply of ethylene-making capacity and the demand for ethylene.