From Ray Dalio:
The economy is like a machine. At the most fundamental level it is a relatively simple machine, yet it is not well understood. I wrote this paper to describe how I believe it works. My description is not the same as conventional economists’ descriptions so you should decide for yourself whether or not what I’m saying makes sense. I will start with the simple things and build up, so please bear with me. I believe that you will be able to understand and assess my description if we patiently go through it.
How the Economic Machine Works: “A Transactions-Based Approach”
An economy is simply the sum of the transactions made and a transaction is a simple thing. A transaction consists of the buyer giving money (or credit) to a seller and the seller giving a good, a service or a financial asset to the buyer in exchange. A market consists of all the buyers and sellers making exchanges for the same things – e.g., the wheat market consists of different people making different transactions for different reasons over time. An economy consists of all of the transactions in all of its markets. So, while seemingly complex, an economy is really just a zillion simple things working together, which makes it look more complex than it really is.
For any market, or for any economy, if you know the total amount of money (or credit) spent and the total quantity sold, you know everything you need to know to understand it. For example, since the price of any good, service or financial asset equals the total amount spent by buyers (total $) divided by the total quantity sold by sellers (total Q), in order to understand or forecast the price of anything you just need to forecast total $ and total Q. While in any market there are lots of buyers and sellers, and these buyers and sellershave different motivations, the motivations of the most important buyers are usually pretty understandable and adding them up to understand the economy isn’t all that tough if one builds from the transactions up.
What I am saying is conveyed in the simple diagram below. This perspective of supply and demand is different from the traditional perspective in which both supply and demand are measured in quantity and the price relationship between them is described in terms of elasticity. This difference has important implications for understanding markets.