  As the first decentralized digital currency introduced in 2009 together with
the blockchain, Bitcoin offers new opportunities both for developed and
developing countries. Bitcoin peer-to-peer transactions are independent of the
banking system, thus facilitating foreign exchanges with low transaction fees
such as remittances, with a high degree of anonymity. These opportunities
together with other key factors led the Bitcoin to become extremely popular and
made its price skyrocket during 2017. However, while the Bitcoin blockchain
attracts a lot of attention, it remains difficult to investigate where this
attention comes from, due to the pseudo-anonymity of the system, and
consequently to appreciate its social impact. Here we make an attempt to
characterize the adoption of the bitcoin blockchain by country. In the first
part of the work we show that information about the number of Bitcoin software
client downloads, the IP addresses that act as relays for the transactions, and
the Internet searches about Bitcoin provide together a coherent picture of the
system evolution in different countries. Using these quantities as a proxy for
user adoption, we identified several socio-economic indexes such as the GDP per
capita, freedom of trade and the Internet penetration as key variables
correlated with the degree of user adoption. In the second part of the work, we
build a network of Bitcoin transactions between countries using the IP
addresses of nodes relaying transactions and we develop an augmented version of
the gravity model of trade in order to identify socio-economic factors linked
to the flow of bitcoins between countries. In a nutshell our study provides a
new insight on the bitcoin adoption by country and on the potential
socio-economic drivers of the international bitcoin flow.
