  The open availability of the entire history of the Bitcoin transactions opens
up the possibility to study this system at an unprecedented level of detail.
This contribution is devoted to the analysis of the mesoscale structural
properties of the Bitcoin User Network (BUN), across its entire history (i.e.
from 2009 to 2017). What emerges from our analysis is that the BUN is
characterized by a core-periphery structure a deeper analysis of which reveals
a certain degree of bow-tieness (i.e. the presence of a Strongly-Connected
Component, an IN- and an OUT-component together with some tendrils attached to
the IN-component). Interestingly, the evolution of the BUN structural
organization experiences fluctuations that seem to be correlated with the
presence of bubbles, i.e. periods of price surge and decline observed
throughout the entire Bitcoin history: our results, thus, further confirm the
interplay between structural quantities and price movements observed in
previous analyses.
