Bitcoin Stock-to-Flow Model Explained and Criticized

The bitcoin stock-to-flow model estimates bitcoin's value from its scarcity, measured as existing supply divided by new annual supply, and it rises in steps at every halving. It became one of the most famous crypto price models after fitting bitcoin's history closely up to 2020, but bitcoin then traded well below the model's implied path in 2021 and 2022, and most analysts now treat it as an interesting idea rather than a reliable forecast.

This guide explains how stock-to-flow works, why it caught on, the main criticisms and how to think about it if you see it cited for 2026 or 2027.

What Stock-to-Flow Means

Stock-to-flow is a concept borrowed from commodities. For gold, the "stock" is all the gold ever mined and still held, and the "flow" is how much is mined each year. Because annual production is tiny compared with existing stocks, gold has a high ratio, which is one reason it's considered a store of value.

Bitcoin's issuance follows a fixed schedule: the block subsidy halves roughly every four years, and total supply is capped at 21 million. Each halving cuts the flow in half, so the stock-to-flow ratio roughly doubles overnight. After the 2024 halving, bitcoin's ratio is higher than gold's by most estimates. Our guide on what the bitcoin halving is explains the schedule.

How the Bitcoin S2F Model Works

The model, published by a pseudonymous analyst known as PlanB in March 2019, plotted bitcoin's market value against its stock-to-flow ratio on a logarithmic scale and found a strong statistical relationship. Fitting a line to that relationship produced a "model price" that steps up at each halving.

Its appeal was clear:

1. 1Simple input. Supply is known in advance, so the model can be projected years ahead.
2. 2Good historical fit. It tracked the 2013 and 2017 cycles reasonably well.
3. 3A compelling story. Scarcity plus halvings equals higher value, which matched the popular four-year bitcoin cycle narrative.

Charts of the model were widely shared during the 2020–2021 bull market, and many investors treated its projected path almost as a schedule. That popularity is part of the lesson: a model that many people believe can shape behavior for a while, then fail abruptly when reality diverges.

Where the Model Failed

The model's implied path for the period after the 2020 halving was considerably higher than where bitcoin actually traded at the end of 2021 and throughout 2022. Bitcoin peaked in late 2021 and then fell by more than three-quarters, far from what the model suggested. Supporters offered explanations, but for many investors the divergence ended the model's credibility as a forecasting tool.

The Main Criticisms

It ignores demand

Price comes from supply and demand. Stock-to-flow only models supply, which is fully predictable. Changes in adoption, interest rates, regulation, ETF flows or investor sentiment, which drive most price moves, are absent from the model.

The relationship may be spurious

Both bitcoin's stock-to-flow ratio and its market value rose over time. Two series that both trend upward can look closely related even if one doesn't cause the other. Statisticians have raised this concern about the model's methodology.

Scarcity doesn't create value alone

Many scarce things have little value. Scarcity matters only if people want the asset. Bitcoin's value depends on continued demand for it as a store of value or medium of exchange.

Diminishing supply effects

With well over 90% of all bitcoin already mined, each halving removes a smaller absolute amount of new supply relative to daily trading volume and ETF flows.

Few data points

The model was built on a small number of halvings. Fitting a curve to a handful of cycles invites overconfidence.

A Quick Comparison of Popular Cycle Models

Our guide to the bitcoin rainbow chart and other cycle charts covers those alternatives.

How to Treat S2F in 2026 and 2027

If you see stock-to-flow cited in forecasts for 2026 or 2027, use it this way:

• As a reminder of supply mechanics, not a price target. Halvings reduce new issuance; that part is fact.
• Combined with demand indicators, such as ETF flows, stablecoin liquidity and sentiment.
• With skepticism toward precise numbers. Any model that outputs a specific price years ahead should be treated as one scenario, not a forecast. See why most crypto price forecasts miss.

Risk Management Instead of Model Faith

Investors who relied heavily on S2F in 2021 often held through steep declines or used leverage expecting the model's path. Safer habits:

• Size positions for a drawdown of more than three-quarters, which has happened repeatedly; see position sizing and risk management basics.
• Take profits in stages rather than waiting for a model's target.
• Avoid leverage based on any model.
• Ignore "guaranteed" model-based schemes, a common hook for scams.

Bottom line

Stock-to-flow captures one real thing about bitcoin: its new supply shrinks on a fixed schedule. But price depends on demand too, and the model's miss in 2021–2022 showed the danger of treating a neat chart as a forecast. Use S2F to understand scarcity, check the live bitcoin price for reality and build your plan around risk, not around a model's line.