Fair issuance is one of the best qualities of Bitcoin. It's not coincidentally impossible to own half the money.

Satoshi is said to have about a million... "only"! Many millions are impossible numbers. When the issuance is slow and competitive, and the holders won't sell, where are the coins going to come from? Hope this answers your question.

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Maybe someone could've gotten to a couple of millions had they had the resources and dedication. Figures like that aren't attainable anymore. There's no market for it, and it would drive the price of bitcoin so high, and the price of whatever you're buying with so low, you'd never come close. All the central bankers combined couldn't get millions of bitcoin.

As for 20 million, there isn't 20 million anymore. Much more than a million has been lost.