  Address clustering tries to construct the one-to-many mapping from entities
to addresses in the Bitcoin system. Simple heuristics based on the
micro-structure of transactions have proved very effective in practice. In this
paper we describe the primary reasons behind this effectiveness: address reuse,
avoidable merging, super-clusters with high centrality, and the incremental
growth of address clusters. We quantify their impact during Bitcoin's first
seven years of existence.
