As bitcoin is nearing its 21-million-unit limit, many voices are saying that buying the cryptocurrency will become much harder, making it more valuable. Others predict that it will cease to become decentralized.

As of January 13th, over 16,800,000 BTC have been mined. It is nearly impossible to pin-point the exact time when all 21 million bitcoins will have been mined. Some think it might be done in a matter of five years, others think that this will not happen in the next 100 years, as mining will increase in difficulty.

At first, there was a 50 bitcoin reward for each mining block. It then dropped 25 bitcoins, and then to 12.5 bitcoins. Considering the halving that occurs every 4 years, by 2020 the block reward will fall to 6.25 bitcoins, thus making it unprofitable.

Once all the existing 21 million have been mined, supply cannot grow, regardless of demand. Some bitcoins will be forever lost or damaged, thus making the supply even smaller. By contrast, the ripple cryptocurrency allows miners to create a maximum of 100 billion tokens.

Blockchain-analysis company Chainalysis, has estimated that 2.78 million to 3.79 million bitcoins have already been lost and will never be recuperated. Bitcoin enthusiasts have said that this will lead to a rapid increase in value, to levels up to $100,000 per token.

Many critics believe that stockpiles of inactive bitcoins exist, these coins belonging to the mysterious Satoshi Nakamoto. It is speculated that these inactive bitcoins will be used to regulate the market like a fiat currency, while Satoshi Nakamoto will act like a central bank.

On Monday, bitcoin had a price of $13,780, more than 30% below its $20, 000 record high. Bitcoin also owns less shares, now owning 33%, compared to the 85% it used to own last year.