  We combine a new, comprehensive database for globular cluster populations in
all types of galaxies with a new calibration of galaxy halo masses based
entirely on weak lensing. Correlating these two sets of data, we find that the
mass ratio $\eta \equiv M_{GCS}/M_{h}$ (total mass in globular clusters,
divided by halo mass) is essentially constant at $\langle \eta \rangle \sim 4
\times 10^{-5}$, strongly confirming earlier suggestions in the literature.
Globular clusters are the only known stellar population that formed in
essentially direct proportion to host galaxy halo mass. The intrinsic scatter
in $\eta$ appears to be at most 0.2 dex; we argue that some of this scatter is
due to differing degrees of tidal stripping of the globular cluster systems
between central and satellite galaxies. We suggest that this correlation can be
understood if most globular clusters form at very early stages in galaxy
evolution, largely avoiding the feedback processes that inhibited the bulk of
field-star formation in their host galaxies. The actual mean value of $\eta$
also suggests that about $1/4$ of the \emph{initial} gas mass present in
protogalaxies collected into GMCs large enough to form massive, dense star
clusters. Finally, our calibration of $\langle \eta \rangle$ indicates that the
halo masses of the Milky Way and M31 are $(1.2\pm0.5)\times 10^{12} M_{\odot}$
and $(3.9\pm1.8)\times 10^{12} M_{\odot}$ respectively.
