Bitcoin’s block reward halves approximately every four years, a mechanism built into Satoshi’s original code. The first halving happened in November 2012, reducing the per-block reward from 50 BTC to 25 BTC. Subsequent halvings in 2016, 2020, and 2024 further reduced issuance to 12.5, 6.25, and 3.125 BTC per block. By design, the total BTC supply will asymptotically approach 21 million.
Each halving has been followed by a major bull market, though whether the halving caused the bull market or merely coincided with it is still debated. The reduction in new supply entering the market does have a mechanical effect: if demand stays constant, reduced supply growth should push prices up. The “stock-to-flow” model, popularized by pseudonymous analyst PlanB, claimed to predict Bitcoin price based on the shrinking supply ratio. The model fit historical data well until it didn’t — prices dramatically diverged from stock-to-flow predictions during the 2022 bear market.
Halvings have also become cultural events. Miners prepare for months, upgrading equipment and negotiating energy contracts to stay profitable at lower rewards. Less efficient miners get squeezed out, shifting hashrate toward newer machines and cheaper power. The 2024 halving, which occurred at block 840,000 on April 20, was particularly eventful because it coincided with the Runes launch, creating unprecedented fee competition on that exact block.
Whether halvings remain as psychologically important to markets over the next two decades is an open question. As block rewards shrink, miners will rely increasingly on transaction fees for revenue. By the 2036 halving, mining economics will look very different than they do today. But for now, the four-year cycle remains the closest thing crypto has to a macro clock. Traders plan for it. Analysts reference it. Entire narratives form around it. Satoshi’s original parameter choice continues to shape the crypto calendar more than fifteen years after mainnet.