Global Ethylene Operating Rates - What Is It Really Telling Me?

Ethylene operating rates are used to indicate the fundamentals of the ethylene market, namely do I have surplus ethylene production capacity to manage supply during global upsets.  Operating rates have been trending higher over the last 6 to 7 years indicating market is getting tighter on ethylene supply.  As we review the historical trend, we need to be aware of the key assumptions driving operating rates for the next 3 to 5 years.  How much capacity are we adding versus demand growth?  Is demand growth real?  What is the feed slate and shall we de-rate more with shift to lighter feeds?  How do on purpose units, MTO/CTO, fit into the mix?  Do plastic recycle trends matter?  Does Polymer substitution incentive grow?  What about coal chemistry to derivatives skipping ethylene?  A change in any one of these assumptions could have dramatic impact on the ability of the system to supply ethylene the market needs.