Proportional symbol maps are a cartographic tool that employs scaled symbols
to represent data associated with specific locations. The symbols we consider are
opaque disks, which may be partially covered by other overlapping disks. We address
the problem of creating a suitable drawing of the disks that maximizes one of
two quality metrics: the total and the minimum visible length of disk boundaries.
We study three variants of this problem, two of which are known to be NP-hard
and another whose complexity is open. We propose novel integer programming formulations
for each problem variant and test them on real-world instances with a
branch-and-cut algorithm. When compared with state-of-the-art models from the
literature, our models significantly reduce computation times for most instances.