The halving is written into the Bitcoin protocol. Rewards went from 50 BTC per block to 25 (2012), 12.5 (2016), 6.25 (2020), and 3.125 (2024). Past cycles saw large rallies in the year after each halving, but four data points are not a law.
It matters because supply growth drops while demand is unchanged, and because the narrative itself moves prices.
Example: after the 2024 halving, daily new supply fell from about 900 BTC to about 450 BTC.
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