  As cryptocurrencies gain popularity and credibility, marketplaces for
cryptocurrencies are growing in importance. Understanding the dynamics of these
markets can help to assess how viable the cryptocurrnency ecosystem is and how
design choices affect market behavior. One existential threat to
cryptocurrencies is dramatic fluctuations in traders' willingness to buy or
sell. Using a novel experimental methodology, we conducted an online experiment
to study how susceptible traders in these markets are to peer influence from
trading behavior. We created bots that executed over one hundred thousand
trades costing less than a penny each in 217 cryptocurrencies over the course
of six months. We find that individual "buy" actions led to short-term
increases in subsequent buy-side activity hundreds of times the size of our
interventions. From a design perspective, we note that the design choices of
the exchange we study may have promoted this and other peer influence effects,
which highlights the potential social and economic impact of HCI in the design
of digital institutions.
