As far as I know lateral stability is usually measured in units of effective dihedral. A high wing airplane with a wing at zero degrees (no dihedal) inherently has a few degrees of effective dihedral due to the keel effect. Swept wing airplanes also have a few degrees of effective dihedral.

So on high wing/swept wing planes (think harrier, C141/C17/C5 etc..) there is too much inherent stability, so the wings are swept down (anhedral) to retain some degree of maneuverability.

Hope that helps some
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I guess I repeated everything said above^

Disregard!