Agustin Carstens, general manager of the Bank for International Settlements (BIS), has renewed his criticism of bitcoin, describing the cryptocurrency as inherently risky and warning that it could become increasingly vulnerable to a 51% attack as it moves closer to its fixed supply cap of 21 million coins.
Speaking at the Hoover Institute on January 27, 2021, Carstens argued that investors should recognize that bitcoin could ultimately fail altogether. His remarks were consistent with his long-standing skepticism toward decentralized cryptocurrencies and with the BIS view that the issuance of digital money should remain primarily in the hands of central banks.
Why Carstens Says Bitcoin Becomes More Fragile Over Time
Carstens suggested that bitcoin’s security model may weaken as new coin issuance declines. In his view, as fewer new bitcoins are produced, the rewards available to miners for processing transactions also fall. That, he argued, could reduce incentives for network participants securing the chain and lead to longer confirmation times. As a result, he said, the system may become more exposed to majority attacks.
The warning goes to the heart of one of the oldest debates around bitcoin: whether a network built on fixed issuance and miner incentives can remain durable over the very long term. Carstens used that debate to reinforce his broader claim that scarcity and cryptography alone are not enough to guarantee that an asset can function reliably as money or as a means of exchange.
His comments did not present new technical data, but they clearly framed bitcoin’s architecture as vulnerable rather than self-sustaining. For Carstens, the issue is not simply volatility or investor speculation; it is whether the network can preserve security and trust as block rewards decline over time.
A Broader Rejection of Bitcoin as Money
Beyond the security question, Carstens characterized bitcoin as a speculative asset lacking “actual value backing.” He argued that bitcoin does not perform the classic functions of money effectively. According to him, its price fluctuations make it unrealistic to use as a unit of account, because goods and services cannot be consistently priced in an asset whose value moves sharply. That same volatility, he said, undermines its utility as a medium of exchange and weakens its credibility as a store of value.
Carstens also took aim at bitcoin mining, saying it consumes more electricity than all of Switzerland. He further pointed to allegations of price manipulation as part of the case against the cryptocurrency. Taken together, those criticisms paint bitcoin, in his view, as a fragile financial phenomenon driven more by speculation and network enthusiasm than by economic fundamentals.
In one of his more dismissive characterizations, he described bitcoin as resembling a “community of online gamers,” underscoring his belief that the asset lacks the institutional grounding needed for a sound monetary system.
Private Stablecoins Also Came Under Fire
Carstens did not limit his criticism to bitcoin. He also challenged the role of private stablecoins, including the Facebook-backed project originally known as Libra and later renamed Diem. His concern was not only about asset backing, but about the legitimacy of private entities operating what could become a public monetary infrastructure.
In his view, privately issued stablecoins backed by fiat currencies or other reserve assets cannot serve as the foundation of a sound monetary system. He argued that such instruments would need to be subject to heavy regulation and close supervision. The underlying principle, he made clear, is that governments must retain control over money issuance and the design of the monetary system.
This criticism reflects a wider policy concern among central banking institutions: that large private payment networks or stablecoin issuers could gain systemic importance without bearing the same public responsibilities as sovereign monetary authorities. Carstens’ remarks therefore fit into a broader institutional push to contain monetary fragmentation and preserve central bank authority.
The BIS View: Central Banks Must Lead Digital Money
Carstens reiterated that if digital money is to exist in a sustainable and trusted form, central banks must play the central role. He argued that only central banks can guarantee stable value, ensure the elasticity of aggregate money supply, and oversee the overall security of the system.
That position aligns closely with the BIS preference for central bank digital currencies, or CBDCs, over decentralized cryptocurrencies or privately issued stablecoins. From this perspective, the challenge is not merely technological innovation, but governance. For Carstens, a payment system must be anchored in public trust, legal accountability, and macroeconomic management—areas where central banks, rather than private issuers or open networks, are seen as the legitimate authority.
His remarks highlight a fundamental divide in the debate over the future of digital finance. Supporters of bitcoin emphasize decentralization, scarcity, censorship resistance, and open access. Institutions such as the BIS prioritize monetary stability, regulated intermediaries, and sovereign control over issuance. Carstens’ speech made clear that, in this debate, he sees bitcoin not as the future of money, but as a risky experiment with structural weaknesses.
Why the Comments Matter
Although the speech dates back to early 2021, the arguments remain relevant because they reflect enduring concerns from one of the world’s most influential international financial institutions. The BIS often serves as a forum for central banks and financial regulators, so comments from its general manager carry weight far beyond a single speech. They offer insight into how traditional monetary authorities view decentralized digital assets and where resistance to crypto-based monetary systems is likely to remain strongest.
At the same time, the speech illustrates how the bitcoin debate continues to operate on two levels: a technical discussion over security, mining incentives, and network design, and a political-economic discussion over who should be allowed to issue money in the digital age. Carstens’ answer is unambiguous—digital money, if it is to become a lasting part of the financial system, must remain under the oversight and authority of central banks.