  Dark markets are commercial websites that use Bitcoin to sell or broker
transactions involving drugs, weapons, and other illicit goods. Being illegal,
they do not offer any user protection, and several police raids and scams have
caused large losses to both customers and vendors over the past years. However,
this uncertainty has not prevented a steady growth of the dark market
phenomenon and a proliferation of new markets. The origin of this resilience
have remained unclear so far, also due to the difficulty of identifying
relevant Bitcoin transaction data. Here, we investigate how the dark market
ecosystem re-organises following the disappearance of a market, due to factors
including raids and scams. To do so, we analyse 24 episodes of unexpected
market closure through a novel datasets of 133 million Bitcoin transactions
involving 31 dark markets and their users, totalling 4 billion USD. We show
that coordinated user migration from the closed market to coexisting markets
guarantees overall systemic resilience beyond the intrinsic fragility of
individual markets. The migration is swift, efficient and common to all market
closures. We find that migrants are on average more active users in comparison
to non-migrants and move preferentially towards the coexisting market with the
highest trading volume. Our findings shed light on the resilience of the dark
market ecosystem and we anticipate that they may inform future research on the
self-organisation of emerging online markets.
