A long time ago, in a different lifetime, I used to work at an industrial plant that operated several 20-ton chemical processes. Our processes operated using a closed-loop system, in the absence of oxygen, and were not pressurized.
We monitored each aspect of our processes using an array of gauges, pressure sensors, thermocouples, and other devices to make sure things were running smoothly at any given point.
Near the midpoint of each process, we had a blowoff valve — a long piece of piping that led to the outside of the building, fitted with a seal that was set to blow out when it reached a certain pounds per square inch (PSI) threshold. The valve was meant to be a safety mechanism so that if, inadvertently, pressure started to build up inside of the process, it would “blow off” outside the building, instead of turning our process into a 20-ton pressure bomb waiting to explode. It’s the same principle that causes a kettle to scream when the steam reaches a certain pressure inside: the whistle only goes off once the water gets hot enough to create enough steam.
Our economy nowadays is similarly a process with lots of variables — though far more toxic than our green process used to be. Regarding our economy, you could throw a dart and pick any variable to monitor: CPI, GDP, the money supply, the price of equities, the price of commodities, or even things like average number of potato chips contained in a $0.99 bag. Just like the economy is trillions of transactions taking place every day, there are similarly an endless number of variables that one could monitor to try and forecast the health of our financial closed loop process.