  We perform a comprehensive measurement analysis of Silk Road, an anonymous,
international online marketplace that operates as a Tor hidden service and uses
Bitcoin as its exchange currency. We gather and analyze data over eight months
between the end of 2011 and 2012, including daily crawls of the marketplace for
nearly six months in 2012. We obtain a detailed picture of the type of goods
being sold on Silk Road, and of the revenues made both by sellers and Silk Road
operators. Through examining over 24,400 separate items sold on the site, we
show that Silk Road is overwhelmingly used as a market for controlled
substances and narcotics, and that most items sold are available for less than
three weeks. The majority of sellers disappears within roughly three months of
their arrival, but a core of 112 sellers has been present throughout our
measurement interval. We evaluate the total revenue made by all sellers, from
public listings, to slightly over USD 1.2 million per month; this corresponds
to about USD 92,000 per month in commissions for the Silk Road operators. We
further show that the marketplace has been operating steadily, with daily sales
and number of sellers overall increasing over our measurement interval. We
discuss economic and policy implications of our analysis and results, including
ethical considerations for future research in this area.
