  As part of on an extensive data mining effort, we have compiled a database of
162 Galactic rotation speed measurements at $R_0$ (the solar Galactocentric
distance), $\Theta_0$. Published between 1927 and 2017 June, this represents
the most comprehensive set of $\Theta_0$ values since the 1985 meta analysis
that led to the last revision of the International Astronomical Union's
recommended Galactic rotation constants. Although we do not find any compelling
evidence of the presence of `publication bias' in recent decades, we find clear
differences among the $\Theta_0$ values and the $\Theta_0/R_0$ ratios resulting
from the use of different tracer populations. Specifically, young tracers
(including OB and supergiant stars, masers, Cepheid variables, H{\sc ii}
regions, and young open clusters), as well as kinematic measurements of Sgr A*
near the Galactic Center, imply a significantly larger Galactic rotation speed
at the solar circle and a higher $\Theta_0/R_0$ ratio (i.e., $\Theta_0 = 247
\pm 3$ km s$^{-1}$ and $\Theta_0/R_0 = 29.81 \pm 0.32$ km s$^{-1}$ kpc$^{-1}$;
statistical uncertainties only) than any of the tracers dominating the Galaxy's
mass budget (i.e., field stars and the H{\sc i}/CO distributions). Using the
latter as most representative of the bulk of the Galaxy's matter distribution,
we arrive at an updated set of Galactic rotation constants, $\Theta_0 = 225 \pm
3 \mbox{ (statistical)} \pm 10 \mbox{ (systematic) km s}^{-1}$, $R_0 = 8.3 \pm
0.2 \mbox{ (statistical)} \pm 0.4 \mbox{ (systematic) kpc}$, and $\Theta_0 /
R_0 = 27.12 \pm 0.39 \mbox{ (statistical)} \pm 1.78 \mbox{ (systematic) km
s}^{-1} \mbox{ kpc}^{-1}$.
