Another day, another article about how logistics capacity will continue to be short into 2022, and perhaps beyond, causing continued supply chain delays and shortages of many consumer products. How can this be, you might ask? wsj.com/articles/u-s-p…
This is something we'll be studying for a while. But to me, it seems like (at least) two forces at play. The first thing to recognize is that logistics capacity--like enormous container ships and ports to unload them--is expensive.
Because it's expensive, there is not a lot of excess capacity during normal operating conditions: this would be wasteful and would raise the cost of global distribution, for companies and consumers alike.
Because of this, global logistics systems are designed to operate at high utilization, modulo some known (predictable) seasonal variations in demand, like the Christmas holiday.
But a port is a classic queueing system. What happens to a high utilization queue when the capacity goes down (due to COVID protocols/labor shortages) and demand goes up (due to increased consumer purchases of manufactured goods)? The queue EXPLODES.
A modest simultaneous increase in demand and decrease in capacity, for a prolonged period of time (so the queue cannot be worked down) could generate the kind of huge backlogs we're seeing: the effect on wait times is highly nonlinear, as my many ops students over the years know. 
The other thing that seems to be happening is the bullwhip effect: consumer demand patterns have changed, and firms, seeing shortages in supply chains, respond by increasing their orders and stockpiling inventory, maybe by more than the amount consumer demand increased.
The bullwhip effect is only going to exacerbate the queueing delays in logistics systems generated by (1) normally high operating utilization and (2) increased utilization, due to decreases in capacity and increases in demand, due to COVID.
All of this is to say: it makes perfect sense that these delays are so extensive. There may be more going on than this, and I am definitely open to seeing more evidence, but it seems like a direct consequence of demand/capacity changes in a highly congested service system.
It continues… wsj.com/articles/suppl…
From the article: “Executives at Lowe’s and Big Lots Inc. have said in recent weeks that they pulled forward holiday imports to mitigate the impact of supply-chain delays. “I think we feel really nicely positioned,” [said] Lowe’s Chief Financial Officer, David Denton.’
This very likely *contributed* to global delays by pulling forward shipments—yet another example of shortage gaming/strategic ordering behavior generating the bullwhip.
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