  We use comparisons between the shapes of gravitational lens galaxies and
models for their mass distributions to derive statistical constraints on the
alignment of the mass distribution relative to the observed lens galaxy and on
the strength of tidal shear perturbations. The mass distributions are aligned
with the luminous galaxies, with a 10 degree upper limit on the rms dispersion
in the angle between the major axes. Statistical constraints, such as our bound
on the misalignment between mass and light, are an important new approach to
reducing the uncertainties in individual lens models, particularly for lenses
used to estimate the Hubble constant.
