Primary Producers are at the center where all loops begin. They grow and raise food so they are not working in an expendable industry.
My maternal grandfather was a farmer who used horses for everything from hauling logs to powering the sulky that took him and Grandma to town. But that all changed when he bought a tractor. Tractors do not eat grass and do not self propagate, so his purchase started a second line of loops that include tractor manufacturers, whose demand for materials created the next level of loops of miners, oil drillers, refiners, service mechanics, you get the picture.
More tractor manufacturers joined in so dealerships sprang up and new loops were formed that managed sales for manufacturing, a services not directly producing food or an object we can see and feel. But soon the dealer no longer had time to sweep out his showroom so he hired a cleaner and yet another loop was created.
Then the cleaner became so busy he hired Jim’s Pooch Grooming Service and now, every Thursday morning, Deefer gets a wash and a brush, her claws trimmed and anal glands expressed and yet another class of loops was added.
We need these loops to create employment as productivity increases and industry continues to automate but we now have more people in outer loops than inner loops and it is these outer loops that are first to go when money gets tight.