What is S2F (Stock 2 Flow) Model ?

In simple terms, the Stock to Flow (SF or S2F) model is a way to measure the abundance of a particular resource. The Stock to Flow ratio is the amount of a resource held in reserves divided by the amount it is produced annually.

The Stock to Flow model is generally applied to natural resources. Let’s take the example of gold. While the estimates may vary, the World Gold Council estimates that around 190,000 tons of gold have ever been mined. This amount (i.e., the total supply) is what we can refer to as the stock. Meanwhile, there are about 2,500-3,200 tons of gold mined each year. This amount is what we can refer to as the flow.

Stock to Flow and Bitcoin

If you understand how Bitcoin works, it won’t be difficult for you to understand why applying the Stock to Flow model to it might make sense. The model essentially treats bitcoins comparably to scarce commodities, like gold or silver.

Gold and silver are often called store of value resources. They, in theory, should retain their value over the long term due to their relative scarcity and low flow. What’s more, it’s very difficult to significantly increase their supply within a short period of time.

According to the advocates of the Stock to Flow model, Bitcoin is a similar resource. It’s scarce, relatively costly to produce, and its maximum supply is capped at 21 million coins. Also, Bitcoin’s supply issuance is defined on the protocol level, which makes the flow completely predictable. You also might have heard about the Bitcoin halvings, where the amount of new supply entering the system is halved every 210,000 blocks (roughly four years).