  We examine world migration as a social-spatial network of countries connected
via movements of people. We assess how multilateral migratory relationships at
global, regional, and local scales coexist ("glocalization"), divide
("polarization"), or form an interconnected global system ("globalization"). To
do this, we decompose the world migration network (WMN) into communities---sets
of countries with denser than expected migration connections---and characterize
their pattern of local (i.e., intracommunity) and global (i.e., intercommunity)
connectivity. We distinguish community signatures---"cave", "biregional", and
"bridging"---with distinct migration patterns, spatial network structures,
temporal dynamics, and underlying antecedents. Cave communities are
tightly-knit, enduring structures that tend to channel local migration between
contiguous countries; biregional communities are likely to merge migration
between two distinct geographic regions (e.g., North Africa and Europe); and
bridging communities have hub-and-spoke structures that tend to emerge
dynamically from globe-spanning movements. We find that world migration is
neither globally interconnected nor reproduces the geographic boundaries as
drawn on a world map but involves a heterogeneous interplay of global and local
tendencies in different network regions. We discuss the implications of our
results for the understating of variability in today's transnational mobility
patterns and migration opportunities across the globe.
