As others have pointed out I believe the composition of American business is an important factor when analyzing historical margins and what may be normal or elevated.

If American business would get a super high concentration of McLanes for some quirky reason it wouldn’t mean that margins were at a cyclical low, it would just mean that American business was now concentrated to an industry where margins are inherently low (but still with decent returns on capital).

Actually I don’t think margins matter as much as returns on invested capital does.
A business with high margins can have low returns on capital and a business with low margins can have high returns on capital.

Competition is what regulates returns on capital. If some factory would earn 30% returns, a new one would quickly be constructed, selling the finished product cheaper to earn an acceptable 15% until industry returns would adjust.

The capital that enters this competitive equation is not on the balance sheet. The balance sheet is just an accounting invention and competition was regulating returns long before accounting was even invented. It is also not the actual capital invested in the business that matters but the capital required for the new guy to build the new factory. It doesn’t matter if someone gave you the factory or if it cost you a trillion dollars. If the new guy can build and earn a decent return the new factory will be built. Replacement cost is what matters when we are talking about what keeps returns on invested capital in check.

Now enter the modern firms, Google, Facebook, Microsoft etc. What is the replacement cost of their intangible assets? Another way to think about it: imagine a world where the balance sheet would accurately reflect replacement cost of the assets through some super calculation (I know but just a thought experiment). In this imaginary world I bet returns on capital wouldn’t look so high.

I have no clue where margins or returns on capital will go from here but I think the above are important considerations for anyone brave enough to put forward a forecast.