Cryptocurrency as an investment or speculation: a bibliometric review study

Purpose – The study was done to review the existing literature available on the theme using a popular technique known as a bibliometric review. The purpose was to explore important bibliometric trends such as geographical distributionofresearch;the mostrelevant countriesand institutions andimportantcollaboration networks, frequently published authors, the most relevant topics/research domains and relationships among these, average citations or per year, the most relevant sources, top authors ’ production, authors ’ impact by H index and the progression of important keywords over a period of time. Design/methodology/approach – The study analyzed literature published in the English language from 2012 onwards that used the words “ cryptocurrency ” , “ Ethereum ” “ Bitcoin ” along with “ investment/s ” or “ speculation/s ” in the Title/ABS/KEY. A specialized approach was followed to retrieve and analyze focused research. The data for analysis was extracted from the Scopus database and was analyzed using Biblioshiny and VOSViewer. Findings – The study found that the countries such as the UK, Australia, China and the USA have special relevance in terms of the number of citations and collaboration networks. Cryptocurrency/Cryptocurrencies, bitcoin have been the base themes along with other crucial issues such as volatility, hedging, COVID-19 pandemic, Ethereum, blockchain, co-integration, portfolio diversification/optimization, spillover, safe haven, investor attention, gold, etc. There is a lot of interdisciplinary research on the theme. Originality/value – The current study used a concentrated approach to study the bibliometric literature about the financial implications of cryptocurrency as an asset class and not prominently its technological or legal aspects.

1. Introduction 1.1 Background Cryptocurrency has been defined using a broad spectrum of technology ranging from virtual complementary currency to electronic currency and its derivative (Dai, 1998).Many cryptocurrencies are based on blockchain technology using a decentralized network of computers.Thus, cryptocurrency is a tradable digital form of money that only exists online and uses encryption to authenticate and secure transactions.Bitcoin was the first currency founded in 2009 by Satoshi Nakamoto to have gained existence in the socio-economic sphere, although the previous attempts such as e-gold in 1996 or liberty reverse in 2006 could not get acceptability (Garcia, Tessone, Mavrodiev, & Perony, 2014).There are currently over a thousand different cryptocurrencies in the world and their supporters see cryptocurrency as the "key to the fairer future economy."(Inci, & Lagasse, 2019).
Cryptocurrencies are an unconventional/unusual, exceptional type of currency due to their decentralized nature but these cannot be used as a substitute for legal currency (Nakamoto, 2008).Cryptocurrency has become popular because of its features such as anonymity, cheaper and faster money transfers and difficulty to counterfeit or blind spending, but there are various disadvantages such as price volatility.Cryptocurrencies have gained a lot of peculiar and numismatology importance (Chohan, 2022), during their short period of existence and are studied by a wide variety of disciplines such as technical aspects like blockchain, cryptography and smart contracts (Xu, Chen, & Kou, 2019), and also from an investment point of view (Saksonova, & Kuzmina-Merlino, 2019).
The study used a concentrated approach to study the bibliometric literature about the financial implications of cryptocurrency as an asset class.Therefore, while retrieving the results, investments/speculation words have been used to narrow down the results and follow a specialised approach to analyze focused results.

Cryptocurrency as an investment or speculation
It is only in the last few years mainly towards the end of 2017; momentum was seen in cryptocurrency exchanges as well as Bitcoin and other prominent cryptocurrencies gained much attention.There has been an increase in the investment in cryptocurrency as a source of investment or speculation because of its high growth potential, highly liquid market, volatile returns, where returns may double also in a couple of days or weeks and it is no longer a niche area of investment.Bitcoin is a very volatile currency but has given good returns to investors (B€ ohme, Christin, Edelman, & Moore, 2015;Fauzi, Paiman, & Othman, 2020).
There is a flip side to it as it is a highly unregulated market and too much volatility may result in returns plunging too low.Not all cryptocurrencies are liquid and there is a lot of risk of money getting locked up.(Chuen, Guo, & Wang, 2017;Thukral, Arora, & Bhandari, 2018;Liew, Li, Budav ari, & Sharma, 2019;Saksonova, & Kuzmina-Merlino, 2019;Mikhaylov, 2020).The greatest advantage and limitation also are that investments are anonymous and "individuals can hold, trade, or use cryptocurrencies instruments without having a direct link with a bank account or any particular investment profile" (Lammer, Hanspal, & Hackethal, 2020, p. 1).
There are various security and privacy risks of investing in Bitcoin (Conti, Kumar, Lal, & Ruj, 2018).Cryptocurrencies are the most recent financial market innovations in terms of infrastructure and support services (FinTech); the use of blockchain technology makes them distinct from traditional investments (Saksonova, & Kuzmina-Merlino, 2017).
These are considered as promising assets in the portfolio but mostly people prefer to use them for short-term gains, that is speculation (Baek & Elbeck, 2015;Baur, Hong, & Lee, 2018;Zhang, Lu, Tao, & Wang, 2021).Like, too much volatility in Bitcoin prices causes speculative bubbles (Cheah, & Fry, 2015) and thus, it has been considered as inefficient asset (Urquhart, 2016).
There is a lack of government intervention and thus, it is subjected to further price distortions; virtual currencies have also been linked to various unregulated activities, including illegal acts (Foley, Karlsen, & Putnin ¸ s, 2019;Griffin & Shams, 2020).Cryptocurrency also impacted investment in other financial assets and some researchers studied dynamic relationships (Corbet, Lucey, & Yarovaya, 2018) and volatility analysis in relation with other assets (Dyhrberg, 2016).
Crypto is a diverse subject area, therefore the current research is focused only on the literature relevant to its being an asset class and not prominently its technological and legal aspects.

Methodology
Bibliometric analysis is a popular and meticulous method for analysing large volumes of scientific publications.It is easy to acquire large volumes of bibliometric data using scientific Cryptocurrency: bibliometric review databases, such as Scopus and Web of Science and the availability of various bibliometric software/tools help to perform the analysis in a logical way.The current study used the Scopus database, which is widely recognized as the largest scientific database of academic significance.The current study analysed studies that used "cryptocurrency or bitcoin or Ethereum" and "investment or speculation" in abstracts/keywords or titles.Cryptocurrency/ bitcoin/Ethereum has been the oldest and the most popular words to represent "Crypto" in the published literature.
The bibliometric analysis summarizes the social and structural relationships between different research constituents (e.g.authors, countries, institutions and topics).The techniques for bibliometric analysis include performance analysis and science mapping.Performance analysis uses citation and publication-related metrics.Performance analysis studies the contributions of research constituents to a given field (Cobo, L opez-Herrera, Herrera-Viedma, & Herrera, 2011;Ramos-Rodr ıgue & Ru ız-Navarro, 2004).The techniques for science mapping include citation analysis, co-citation analysis, bibliographic coupling, co-word analysis and co-authorship analysis (Baker, Kumar, & Pandey, 2021;Cobo et al., 2011;Ramos-Rodr ıgue & Ru ız-Navarro, 2004).

Research objectives
The purpose of this research is to study the research articles on the theme to identify the relevant bibliometric trends such as: (1) To identify the geographical distribution of research and the most relevant countries and institutions researching the theme and their collaboration networks.
(2) To find out the frequently published authors, the most relevant topics, the number of publications by country, average citations per year, the most relevant sources, top authors' production, authors' impact by H index and trending topics.
(3) To identify the important research domains/topics and the relationships among them.
(4) To find out the progression of important keywords to understand the impact of changes in economic and political environments on research trends over a period of time.

Data extraction
Earlier studies have done the bibliometric analysis of CRYPTO from its overall perspective (Dabbagh, Sookhak, & Safa, 2019;Shen, Chang, & Su, 2018; Garc ıa-Corral, Cordero-Garc ıa, de Pablo-Valenciano, & Uribe-Toril, 2022).Crypto is a riskier asset class with numerous drawbacks but still, it became popular because of its profitability.The current study used investment or speculation as a part of the search criterion to extract only the relevant literature and to exclude the studies which focused mainly on the other aspects of Crypto.
To perform the bibliometric performance and science mapping analysis, the following steps for data extraction were used (Figure 1):

Data analysis
Biblioshiny and VOSViewer has been used to analyze the data.Biblioshiny is a web-based graphical interface powered by Bibliometrix (Aria, & Cuccurullo, 2017).Bibliometrics was programmed in the R language and it has interconnection with other R packages.Different mapping techniques have been used (Boyack, Klavans, & B€ orner, 2005) in Biblioshiny.VOSViewer is a software tool based on Java programming language for creating maps for bibliometric purposes (version 1.6.18 was used).VOSViewer provides three visualizations, BAJ 44,1 referred to as network visualization, overlay visualization and density visualization (Van Eck & Waltman, 2019).The three different indicators have been used for the analysis of documents: quantity, quality, structural form and other bibliographic information of publications.Quantity shows the productivity index in terms of the number of publications.Meanwhile, quality shows the impactful articles on the basis of the number of citations received.

Preliminary bibliographic information
Scopus database search applied from 2012 to 2021 and sorted out using the criterion mentioned in the data extraction steps (Figure 1).The summary results are presented in Table 1.
We can notice the huge momentum in the overall number of publications from 2019 onwards (Figure 2).The subject areas of economics, econometrics and finance have got the highest ranking (29.88%), followed by business, management and accounting (14.6%) and then, followed by computer science (14.04%).The remaining articles are distributed among varied subject areas, that is, engineering, mathematics; the social sciences, decision sciences, physics and astronomy, material sciences, energy, environmental, multi-disciplinary, arts and humanities, chemicals, even agriculture, neuroscience, etc. (Figure 3).

The most cited articles
Applying the corresponding search results, we found that the top three articles that have been cited the most are on the volatility aspect of the bitcoin.The article "BitCoin meets Google Trends and Wikipedia: Quantifying the relationship between phenomena of the Internet era" (Kristoufek, 2013) is about semantic analysis.The top-cited articles have used "bitcoin" in the title of the papers, which shows the Bitcoin was more popular as compared to the other cryptocurrencies.The most cited topics have been related to volatility/speculation, price formation/trends, security and privacy concerns, and the relationship with other financial assets/hedging capabilities of the Bitcoin (Table 2).

Geographical distribution
In terms of geographical distribution, an apparent growing trend of research is originating all over the world.(Figures 4 and 5).A minimum of three documents and three citations have been used to draw the map.The UK, Australia and China have been the front-runners in terms of grouping and citations.Cryptocurrency: bibliometric review

Pivotal institutions
The highest ranking among the pivotal institutions is of "DCU Business School, Dublin City University, Dublin 9, Ireland" with a total of 14 documents, 992 citations, and 208 link strengths.This institution is followed by "Trinity Business School, Trinity College Dublin, Dublin 2, Ireland" with a total of 10 documents, 890 citations, and 204 link strengths.Again, in terms of the number of published documents, the next ranked institutions are "USEK Business School, Holy Spirit University Of Kaslik, Jounieh, Lebanon" with 11 documents, but has the highest number of citations as 1,032; "Montpellier Business School, Montpellier, France" with a total of ten documents and 737 citations, and "Department Of Economics And Finance, College Of Economics and Political Science, Sultan Qaboos University, Muscat, Oman" with a total of seven documents and 310 citations.A minimum of three documents and three citations have been used to draw the map (Figure 6).Thus, European countries, mainly Ireland and France are doing extensive research.

Top journals
Table 3 and Figure 7 shows the sources on the basis of citations.To draw the map, the minimum number of documents and citations was fixed at five.Finance Research Letters, Economics Letters, International Review of Financial Analysis and Research in International Business and Finance are the pioneer journals that have worked on the topic.

Prominent authors
Table 4 and Figure 8 show the author's order according to the number of articles on the topic.E. Bouri, D. Roubaud and S. Corbet have been leading on the basis of number of publications, H Index, and Total Citations.Y. LI has a large number of articles but the citation is less as compared to the other three authors.Figure 9 shows that both the top authors E. Bouri and D. Roubaud have also collaborated extensively.Similarly, S. Corbet and B. Lucey have good collaboration with each other.BAJ 44,1 "blockchain, investments, bitcoin, Ethereum" and author's keywords as "cryptocurrency, bitcoin, blockchain, COVID-19".The conceptual structure map (Figure 12) Of the MCA keyword plus shows two main clusters in different colors that coincide with the driving theme of these publications.According to the conceptual structure, the research is largely on topics like forecasting, time series analysis, alternative asset classes such as gold, COVID-19, price dynamics/prediction, stock market, empirical analysis, financial system/market, internet and electronic commerce and the technological evolution such as machine learning.

Thematic map
Porter's derivation algorithm has been used for thematic maps to reduce the number of words used in a root form.Both show that regardless of the analysis used and keywords, the central topics are bitcoin, cryptocurrency, stock market and investments, and other important themes are Ethereum, blockchain network and electronic money (Figure 13).
Figure 14 shows a thematic division into three different periods on the basis of the title of the articles.Cryptocurrency, bitcoin, network/internet and digital have been the most frequently used words in the titles of articles.From 2012 to 2015, bitcoin was the most important cryptocurrency and most of the work has been done on it during this period.From 2016 to 2020, "blockchain" picked up, and from 2020 to 2022, "COVID-19" has been used Cryptocurrency: bibliometric review frequently in the titles of articles.Figure 15 shows a thematic division into four different periods on the basis of keywords plus.Since 2016, cryptocurrency and investment have been used as keywords.Then, the environment, crime, blockchain technology, intelligent systems and COVID-19 became popular keywords.Lot of research is also done on crime relate aspects of investments in these assets (Turner, McCombie, & Uhlmann, 2019;Albrecht, Duffin, Hawkins, & Rocha, 2019).Based on the blockchain network analysis, this technology and smart contracts are potential areas in cryptocurrency-related studies (Xu et al., 2019;Chang, Chen, & Lu, 2019).

Summary and conclusions
The study analysed the bibliometric trends from 2012 onwards.Bibliometric information was extracted from the Scopus database.The search criterion was "cryptocurrency", "Ethereum" or "Bitcoin" along with "investment/s" or "speculation/s" in the Title/ABS/KEY to get the concentrated results.The results show a positive evolution in terms of the number of articles published and citations with a growing interest and relevance in recent years (Table 1 and Figure 2).The main topics or research areas that contain concepts related to cryptocurrency are in the subject areas of economics, econometrics and finance (Figure 3).
The countries such as the UK, Australia, China and the USA, stand out in terms of citations and groupings.Asian continent is emerging as a potential researcher on the basis of geographical analysis.A more in-depth analysis shows that the main journals and authors belonging to the ranking also belong to the countries with the highest number of publications  3).E. Bouri, D. Roubaud and S. Corbet have been the most influential authors in terms of the number of publications, H Index and total citations ( Table 4 and Figures 7-9  Cryptocurrency/Cryptocurrencies, bitcoin have been the base themes along with other critical issues such as volatility, hedging, COVID-19 pandemic, Ethereum, blockchain, co-integration, portfolio diversification/optimization, spillover, safe haven, investor attention, gold, etc (cluster map; Figure 10 and three fields plot; Figure 11).Interdisciplinary studies involving the use of technology, criminology, philosophy and psychology along with basic subject areas of commerce/business and finance have great potential for future researchers (conceptual structure; Figure 12).The current study also found that the earlier studies were mostly related to the speculative nature of cryptocurrency/bitcoin.The trend of the present research is wide and varied such as diversification, linkages with other assets, hedging and investment patterns (thematic maps; Figures 13,14 and 15).Table 2 (top ten most cited articles) shows research on areas such as risk, volatility, inefficiency, speculative bubbles, security features, price formation and hedging.The trend of the bibliometric research shows there is lot of research on Crypto as a short-term asset and its speculation benefits and other associated risks/linkages, etc.There is hardly any research where in Crypto has been studied as a long-term investment asset.Thus, Crypto might be profitable as a speculative asset but it is not suitable for long-term investment purposes.
The study has some limitations.Firstly, the field of studies is based on only one academic database and that is Scopus.Secondly, the type of document included in the analysis has been limited to articles.The use of other important databases, such as Google Scholar and Web of Sciences, could have been used for wider coverage of the articles.
There is a lot of risk in cryptocurrency as the market is highly volatile and it is subject to bubbles in cryptocurrency markets (Corbet et al., 2018;Cheah and Fry, 2015;Urquhart, 2016).Cryptocurrencies' basic security model might not be reliable (Auer, 2019).There is ample debate on the legal nature of cryptocurrencies, as well (Fr€ owis & B€ ohme, 2017;Walch, 2019).Investors may also consider regular rebalancing of the portfolio, which could help increase its profitability (Saksonova, & Kuzmina-Merlino, 2019).
The research provides an opportunity to explore the important bibliometric trends on the theme.Future researchers can benefit in terms of identifying potential research topics.Cryptocurrency has been challenging to deal with for all the Governments across the world in spite of issuing various advisories.The author recommends that cryptocurrency is a risky asset class as explained in the paper; therefore, avoidance is the best approach for investors seeking a perspective over the long term.
Figure 1.Data extraction steps

Figure 3 .
Figure 3. Distribution by subject area (Pareto chart) Figure 4. Geographical distribution Figure 5. Grouping by country and citations

Figure 7 .
Figure 7. Cluster map of journals (sources) on the basis of citations and total link strength

Figure 10 .
Figure 10.Cluster map on the basis of the author's keywords ).
Figure 11.Three fields plot on the basis of keywords plus, sources and the author's keywords

Table 2 .
These countries also account for the largest number of articles and citations together with the highest H indexes.According to the map, India formed a cluster with United Arab Emirates, South Africa, Saudi Arabia, Poland, Indonesia Egypt and Malaysia.The USA and the Czech Republic are the two other notable countries in terms of grouping and citations.The UK, Australia, China and the USA clearly stand out in terms of citations and groupings.Top ten the most cited articles Source(s): Author's own compilation from the Scopus database

Table 4 .
Scopus database: author's own compilation using R studio Distribution