  Two different simple measurements of galaxy star formation rate with
different timescales are compared empirically on $156,395$ fiber spectra of
galaxies with $r<17.77$ mag taken from the Sloan Digital Sky Survey in the
redshift range $0.05<z<0.20$: a ratio $\Aamp / \Kamp$ found by fitting a linear
sum of an average old stellar poplulation spectrum (\Kamp) and average A-star
spectrum (\Aamp) to the galaxy spectrum, and the equivalent width (EW) of the
$\Halpha$ emission line. The two measures are strongly correlated, but there is
a small clearly separated population of outliers from the median correlation
that display excess $\Aamp /\Kamp$ relative to \Halpha EW. These ``K+A'' (or
``E+A'') galaxies must have dramatically decreased their star-formation rates
over the last $\sim 1$ Gyr. The K+A luminosity distribution is very similar to
that of the total galaxy population. The K+A population appears to be
bulge-dominated, but bluer and higher surface-brightness than normal
bulge-dominated galaxies; it appears that K+A galaxies will fade with time into
normal bulge-dominated galaxies. The inferred rate density for K+A galaxy
formation is $\sim 10^{-4} h^3 Mpc^{-3} Gyr^{-1}$ at redshift $z\sim 0.1$.
These events are taking place in the field; K+A galaxies don't primarily lie in
the high-density environments or clusters typical of bulge-dominated
populations.
