The Bitcoin Halving The Bitcoin code includes a built-in mechanism to limit the total number of bitcoins. Governed by algorithm, the protocol generates new bitcoins at a fixed rate: a fixed number of coins every ~ten minutes . This implies a steady increase in the coin supply. But there's a second half to that algorithm: every four years, the per-ten-minute reward is halved. This ensures that the emission rate of the coin eventually reduces to what becomes effectively zero. Since this creation rate is halved each cycle, the event surrounding this reduction is referred to as the halving. The third such halving event will occur on or about May 12th. At that moment, each new Bitcoin block will then include 6.25 newly mined (minted) bitcoins compared to the 12.5 mined for each block now. Interestingly, this will be the first time that Bitcoin's monetary inflation rate will be under the Federal Reserve's 2% target for price inflation.

The History Historically, Bitcoin halvings have been quite uneventful. I teach at the collegiate level; I distinctly remember being between two classes when the first halving occurred. As the event approached, I was engrossed, staring at my computer screen, as I watched each new block being generated. The busy college campus hummed along blithely unaware as first a block was generated with a 50 bitcoin reward, and then in the next moment, a 25 bitcoin reward. Blockchain.info thoughtfully displayed some fireworks on the screen at precisely that historic moment. Shortly thereafter, my students convened for their algebra class: not a single mention, by anyone, of the event for which I was so excited. From a technical standpoint, the whole flow of events was impressive. I was impressed that humans could write a program that dictated the behavior of a network years into the future. The effect of the halving—and the corresponding supply reduction it represents—to bitcoin's pricing, was difficult to discern in those first couple four-year iterations. There were price spikes six months after each halving, but whether there was a causal relationship, we simply don't know. A correlation does not automatically imply a causal relationship.

Analysis Here's the thought process I went through in November of 2012. I made the following assumptions: Bitcoin is a currency.

Demand for bitcoin is a constant. Today, the first assumption is no longer valid as the number of transactions can no longer support the currency use case. The second assumption I considered, at least at the time, to be a conservative one. I measured the demand for bitcoins as the amount of money it took to buy the newly mined coins—their value, in fiat. Long run Given these assumptions, one would expect the price of bitcoin to double eventually. This assumption had me hopeful about the future price of bitcoin. But I wasn't happy with 'eventually.' I wanted to know just how quickly this doubling would occur? How Long is the Long Run? In 2012, the price of one bitcoin was around $10. Therefore, for each 50 bitcoins generated, there was an associated $500 cost burden when they were sold on the open market — $500 every ten minutes. After the halving, only $250 would be needed to buy each new allotment of 25 bitcoins, leaving $250 of unmet demand fed into the market cap. Or I at least assumed. $250 every 10 minutes comes to $1.08 million per month. If this were factored into the market cap algebraically, about 0.01 would be added to the price of bitcoin in the next month. So, with these assumptions, the price should eventually double, but it would take a great deal of time. Using today's numbers, the time required to double again would be even longer. Much longer. Further Considerations Note, even if the analysis found that the price would increase dramatically, the psychological aspects of the bitcoin market may thwart the doubling at the mathematically predicted time frame. When investors are alerted to a likely rise in price, it stands to reason that rational actors would buy that item before the expected price increase. This price pressure (sudden demand) would then increase the price prematurely.