##coin is limited to 21 million units by 2040. in the long run, a fixed money supply may harm the macroeconomy by contributing to deflation in the prices of goods and services, and in wages. and the inability of the money supply to vary in response to demand would likely cause greater volatility in prices and real activity. as the italian philosopher george santayana famously observed. all speeches are available online at www. bankofengland. co. uk / speeches in the short run, the fixed supply of bitcoin has fed a global speculative mania that has encouraged a proliferation of new cryptocurrencies. as my colleague agustin carstens has argued, this surge of competitors and the “ forking ” of bitcoin echoes the debasement of private monies in the past. inefficient media of exchange the most fundamental reason to be sceptical about the longer term value of cryptocurrencies is that it is not clear the extent to which they will ever become effective media of exchange. currently, no major high street or online retailer accepts bitcoin as payment in the uk, and only a handful of the top 500 us online retailers do. for those who can find someone willing to accept payment for goods and services in cryptocurrencies, the speed and cost of the transaction varies but it is generally slower and more expensive than payments in sterling. that ’ s because the more heavily used cryptocurrencies face severe capacity constraints compared with other payment systems. for example, visa can process up to 65, 000 transactions per second globally against just 7 per second for bitcoin. and if you use a debit or credit card in the uk, the transaction is completed in seconds and without exchange rate risk. in contrast, bitcoin users can face queues of hours. those wanting to get to the front to make time - pressing payments – for last orders, for example – need to offer up a transaction fee sufficiently large to persuade bitcoin “ miners ”, who verify and process transactions, to do so quickly. the fees paid vary through time, but reached £40 in late 2017. fees are currently around £2, but even that is expensive relative to cash, cards or online payments which cost the retailer around 1. 5 pence, 8 pence and 19 pence respectively. over time, bitcoin transaction fees could rise further because the subsidy miners enjoy by being partly paid with

private sector to explore the scope for cross - border payments in central bank money through synchronised national rtgs systems. this all could increase the speed and safety, as well as lower the costs, associated with cross - border transactions to support purchases and travel overseas. when coupled with the capture of richer payments data made possible by its renewal, rtgs will help support innovative services for the more effective management of personal and company finances. these benefits will be amplified by the uk ’ s ambition in implementing the open banking standard – under which the largest banks will be required to make customer data available to other existing firms and innovators, if the customer demands. in turn, this will help improve aggregator, comparison and switching services. taken together, these advances will support innovation that allows you to manage your finances seamlessly, from tracking how much you spend on beer and books, to managing your future savings and current loans. psr indirect access market review, https : / / www. psr. org. uk / sites / default / files / media / pdf / mr1512 - indirect - access - market - reviewinterim - report. pdf all speeches are available online at www. bankofengland. co. uk / speeches finally, at the wholesale payments end, we ’ ve already explored whether the core of the new rtgs system could run on distributed ledger to discover that the technology is not yet sufficiently mature or reliable to run a system that settles the equivalent of a third of the uk ’ s annual gdp each day and requires 5 - sigma performance. nonetheless, the bank believes that distributed ledger technology could over time significantly improve the accuracy, efficiency and security of processes across payments, clearing and settlement. securities settlement in particular is ripe for innovation. transactions that take nanoseconds to execute, currently take days to settle along a chain involving many intermediaries. at stake, are the tens of billions of pounds of capital that are tied up while settlement completes. the best in the private sector are working hard unlocking this value. that ’ s why the bank is building the new rtgs so that new forms of securities settlement that meet our standards of resilience ( including those using distributed ledger ) will be able to plug in directly. ultimately this combination of new technology and direct access to rtgs could be applied to other assets such as helping make the payment, registration and stamp duty processes involved in house purchases quicker and more efficient. the future of money while adam smith