  We study the role of average concurrence in entanglement swapping in quantum
networks. We begin with qubit pure states, and there is a very simple rule
governing the propagation of average concurrence in multiple swaps. We look at
examples of mixed qubit states, and find the relation for pure states gives an
upper bound on what is possible with mixed states. We then move on to qudits,
where we make use of the I-concurrence. Here the situation is not as simple as
for qubits, but in some cases relatively straightforward results can be
obtained.
