  Many real-world complex systems across natural, social, and economical
domains consist of manifold layers to form multiplex networks. The multiple
network layers give rise to nonlinear effect for the emergent dynamics of
systems. Especially, weak layers that can potentially play significant role in
amplifying the vulnerability of multiplex networks might be shadowed in the
aggregated single-layer network framework which indiscriminately accumulates
all layers. Here we present a simple model of cascading failure on multiplex
networks of weight-heterogeneous layers. By simulating the model on the
multiplex network of international trades, we found that the multiplex model
produces more catastrophic cascading failures which are the result of emergent
collective effect of coupling layers, rather than the simple sum thereof.
Therefore risks can be systematically underestimated in single-layer network
analyses because the impact of weak layers can be overlooked. We anticipate
that our simple theoretical study can contribute to further investigation and
design of optimal risk-averse real-world complex systems.
