# From Bitcoin to Central Bank Digital Currencies: Making Sense of the Digital Money Revolution
## 3 Experiments, Proofs-of-Concept, and Pilots  
Before 2016, most central banks had not yet proceeded to actual CBDC experiments. For example, the Bank of China, which is nowadays at the forefront of retail CBDC implementation, started seriously exploring the concepts only in 2014 [55]. According to the dataset of [56], updated to April 2021, over 55 countries conducted retail CBDC experiments and, of those, at least 20 created pilots (mainly in the last two years) and three central banks/monetary areas supposedly launched their CDSCs to general availability. Earlier experiments focused primarily on wholesale CBDCs rather than the retail variant [57; 58]. While most of the experiments had a national scope, a few also evolved to support cross-border cooperation, namely Project Stella [59] and Projects Jasper/Ubin (Bank of Canada and Monetary Authority of Singapore). However, retail CBDCs are the ones garnering more interest of late. Of the more advanced generally available CDSCs,  
Figure 1: The money flower: a taxonomy of money; source: [43; 51]. the Bahamas Sand Dollar, launched in 2020 [60], is arguably the first generally available retail CDBC. This currency is pegged to the Bahamas Dollar, which in turn is pegged at a 1:1 ratio to the USD. This early interest can illustrate the need for smaller central bank currencies pegged to more significant ones to act proactively in the CBDC domain, otherwise risking replacement by electronic transactions using the stronger currency. According to several [61; 62], the only large economy to launch a retail CBDC so far is China, with its e-CNY/DCEP (Digital Currency Electronic Payment). However, although it has been made available in certain areas in early 2021, it is still in pilot, and full adoption is expected only after 2023 [63], even though proofs of concept of increasing breadth have been proceeding, including the proposal of its availability for attendees of Beijing's 2022 Winter Olympics. Finally, on 31 March 2021, the DCash was launched as a pilot open to the public by the East Caribbean Central Bank [64]. This currency is also indirectly pegged to the USD via the East Caribbean Dollar (although not at a 1:1 ratio). In the latest survey by the BIS, over 85% of banks admitted to exploring the advantages and drawbacks of CDBC [65]. CDBCs involve a very diversified set of actors and initiatives on different stages of maturity, graphically depicted in ([58], p. 3). The worldwide interest in CBDCs is also visible in Google Trends search data results for the expression \"Central Bank Digital Currency\" [66]. A steep increase is noticeable in the most recent years. To reduce seasonality effects, we present the monthly data averaged by quarter in Figure 2.  
Although the number of CDBC experiments and pilots may give an idea of homogeneity, this is far from true. Many variations are present in the different approaches, and we can find several independent attempts to create taxonomies [67; 68; 69] to characterize the approaches followed by the different central banks. Table 2 shows a set of characteristics that CDBCs may possess. Notice that the experiments and pilots may include CDBCs pursuing just one (the most common case) or several alternative characteristics. Figure 2: Evolution of search interest in CDBC and Central Bank Digital Currency (CBDC), worldwide, in Google Trends, monthly data averaged by quarter; Source: authors’ own. While no full data are available to perform a comprehensive matching of current central bank initiatives with the design goals of Table 2, using the dataset from [56; 65], after removing duplicates and projects without information on three or more characteristics, some patterns emerge. From the remaining 20 CDBC projects, most are exploring either indirect (11) or hybrid (14) architectures, with direct claims in only four projects. The numbers do not add to 20 since three experiments do not declare architectures and others explore more than one.