On December 31, Cai Weide, a nationally-appointed professor and a guide from Beihang University, published an article in China Financial Information Network, "Blockchain: A Chance for a Powerful Science and Technology Nine Years". The article said that once the country issues digital fiat currency, it can be profitable. The payment system market is 3 trillion, and it will increase to 6 trillion in the future. The trade finance is 22 trillion, while the US GDP is 21.8 trillion and the UK GDP is 2.8 trillion. So we can see the market of payment system and trade financial system It is huge. If digital fiat currency is used in trade finance, as long as there is a 13% market, it will exceed British GDP. In this way, the UK does not need to increase any products, nor does it need to increase the issuance of sterling, to double its GDP.