Plan B and the Bitcoin Stock-to-Flow Model

Definition

The Stock-to-Flow (S2F) model, popularized by the anonymous analyst known as Plan B, is a quantitative model that endeavors to forecast the long-term price trajectory of Bitcoin. It operates on the fundamental economic principle of scarcity, suggesting that assets with a high stock-to-flow ratio—meaning a large existing supply relative to a low rate of new production—tend to hold or increase their value over time. For Bitcoin, this model specifically links its price to its inherent digital scarcity, which is algorithmically controlled and predictable.

The Stock-to-Flow (S2F) model is an economic framework that quantifies the scarcity of an asset by dividing its total existing supply (stock) by its annual production rate (flow), often used to predict the long-term price of scarce commodities like gold, silver, and Bitcoin.

Key Takeaway

The S2F model posits that Bitcoin's increasing scarcity, primarily driven by its programmed halving events, should lead to a predictable increase in its market value over time. While historically influential and initially demonstrating a strong correlation with Bitcoin's price movements, its predictive accuracy has faced significant scrutiny and challenges, particularly in recent market cycles. Investors and traders should understand its underlying mechanics and historical context, but also be aware of its limitations and the criticisms it has garnered, especially concerning its lack of demand integration.

Mechanics

The core of the Stock-to-Flow model lies in its simple yet powerful ratio: Stock divided by Flow. For Bitcoin, the "stock" refers to the total circulating supply of BTC that has been mined and is currently in existence. The "flow" represents the annual rate at which new Bitcoins are introduced into the supply through mining rewards. This annual flow is a crucial component because it is directly impacted by Bitcoin's halving events, which occur approximately every four years.

During a halving, the reward for mining a new block is cut in half, effectively reducing the annual "flow" of new Bitcoins. When the flow decreases while the stock continues to grow (albeit at a slower rate), the S2F ratio increases. The model then extrapolates a potential price based on this increasing scarcity ratio. The underlying assumption is that, similar to traditional scarce commodities like gold and silver, an asset's value is directly proportional to its scarcity. Bitcoin's predictable and decreasing issuance schedule makes it a unique candidate for such a model. The S2F deflection is a related metric that measures how far the current Bitcoin price deviates from the price predicted by the S2F ratio, offering insights into whether Bitcoin is over or undervalued according to the model.

Trading Relevance

For many years, the Stock-to-Flow model served as a significant tool for long-term investors and traders seeking to understand Bitcoin's potential price trajectory across market cycles. It provided a compelling narrative for Bitcoin as a deflationary asset and a form of digital gold, whose value would naturally appreciate due to its programmed scarcity. Traders often used the model's projections to establish long-term price targets, inform their accumulation strategies, and gauge the overall health of a bull market, particularly in the periods following a halving event.

However, its relevance in active trading has evolved. While it still offers a macro perspective on Bitcoin's supply dynamics, its direct utility for short-term trading signals is limited. Experienced traders understand that the S2F model primarily focuses on the supply side of the equation, often overlooking the complex interplay of demand, macroeconomic factors, regulatory developments, and market sentiment that drive short-to-medium term price action. Therefore, while it can contribute to a broader understanding of Bitcoin's long-term value proposition, it is rarely used in isolation for making immediate trading decisions. Instead, it is often considered alongside other valuation frameworks, such as the Bitcoin Power Law Chart and various on-chain indicators, to form a more comprehensive market view.

Risks

The Stock-to-Flow model, despite its initial appeal, carries several significant risks and has faced substantial criticism, particularly as Bitcoin's market matures. The primary risk stems from its lack of demand integration. The model is purely supply-side driven; it assumes that demand for Bitcoin will always be sufficient to absorb the decreasing supply at ever-higher prices. However, Bitcoin's price is a function of both supply and demand, and external factors such as global liquidity, institutional adoption, regulatory crackdowns, technological advancements, and shifts in investor sentiment can profoundly impact demand, which the S2F model does not account for.

Furthermore, the model has demonstrated increasing deviations from actual price. While it showed remarkable accuracy for several years, it has recently missed its targets by significant margins. For instance, in 2025, the model's average price projection reached a staggering $500,000, while Bitcoin's actual price hovered around $120,000 as of August 11, 2025. This substantial discrepancy has led critics to declare the model's eventual failure, with some predicting its breakdown by 2026. Over-reliance on the S2F model can lead to unrealistic price expectations and poor investment decisions, especially if market conditions do not align with its scarcity-driven assumptions. Plan B himself has reportedly lamented the "strange, flat bull market" that, despite a price increase of over $100,000 from its November 2022 low of $15,000, did not show the momentum expected by the model. This highlights the danger of relying on a single, incomplete model that cannot fully capture the complexity of the crypto market.

History and Examples

The Stock-to-Flow model was introduced in 2019 by the pseudonymous analyst Plan B and quickly gained popularity within the crypto community. It was based on the observation that Bitcoin, much like traditional scarce assets such as gold and silver, exhibits a high stock-to-flow ratio, and its price performance historically correlated with this ratio. The model's early successes, particularly its apparent ability to accurately predict Bitcoin's price trajectory over several years, significantly contributed to its credibility. Key halving events in 2012, 2016, and 2020 served as crucial data points, demonstrating a reduction in supply followed by price appreciation, seemingly in line with the model's projections.

A prominent example of the model's challenges is the period following the Bitcoin crash of 2022. While Bitcoin recovered from its low of $15,000 in November 2022 to approximately $120,000 by August 2025, the S2F model's projected average price for 2025 was $500,000. This significant deviation of over 300% between the actual price and the model's forecast has starkly highlighted the limitations of the S2F model. Critics, such as Francis Tapon, pointed out eight flaws in the model as early as 2020 and predicted its ultimate failure by 2026. Although the model might survive until the next halving due to its wide range of acceptable values, its ability to make precise predictions is increasingly questioned, diminishing its historical relevance as a standalone forecasting instrument.

Common Misunderstandings

A widespread misunderstanding is that the S2F model is a definitive price forecast or a guaranteed roadmap for Bitcoin's value appreciation. In reality, it is a probabilistic model based on historical data and the assumption that scarcity is the primary value driver. It offers a potential long-term valuation, but not an exact or guaranteed price prediction for any specific point in time. The reality of the crypto market is far more complex and influenced by a multitude of unpredictable factors.

Another common misconception is the belief that the S2F model accounts for all relevant market factors. It focuses almost exclusively on the supply side, largely ignoring demand dynamics, macroeconomic shocks, regulatory changes, technological innovations, or broader investor behavior. These external forces can significantly impact Bitcoin's price, causing the model to deviate from reality. Finally, it is often mistakenly assumed that the S2F model is universally accepted. While it gained popularity within the crypto community, it has faced considerable criticism in academic and analytical circles, particularly regarding its statistical robustness and the simplicity of its underlying assumptions. It is one tool among many and should not be understood as the sole truth about Bitcoin's value, but rather as a perspective that must be considered in the context of other analyses.

Summary

Plan B's Stock-to-Flow model represented a groundbreaking attempt to understand Bitcoin's value progression through the lens of scarcity. It provided a compelling narrative and a visual representation that attracted many investors during Bitcoin's early growth phases. Its initial ability to correlate price movements over several years lent it significant credibility and established it as an influential model in crypto analysis.

However, with time and the increasing maturity of the Bitcoin market, the limitations of the S2F model have become apparent. Its exclusive focus on supply and its neglect of demand dynamics, as well as broader macroeconomic influences, have led to significant deviations from actual prices. While it continues to offer an interesting perspective on Bitcoin's scarcity value, it should not be regarded as a sole or infallible forecasting instrument. Instead, it serves as one element within a broader spectrum of analytical tools, which must be complemented by critical evaluation and the consideration of diverse market indicators to make informed decisions in crypto trading.