  We present the luminosity function and color-redshift relation of a
magnitude-limited sample of 145 mostly red field E/S0 galaxies at z < 1 from
the DEEP Groth Strip Survey (GSS). Most of the E/S0s (86%) form a red envelope
in the redshift-color diagram, consistent with predictions of spectral
synthesis models in which the dominant stellar population is formed at
redshifts z > 1.5. Constructing a luminosity function of the full sample of
  145 E/S0s, we find that there is about 1.1--1.9 magnitude brightening in
rest-frame B band luminosity back to z = 0.8 from z=0, consistent with other
studies.
  Together with the red colors, this brightening favors models in which the
bulk of stars in red field E/S0s formed before z_{for} > 1.5 and have been
evolving rather quiescently with few large starbursts since then.
  Evolution in the number density of field E/S0 galaxies is harder to measure,
and uncertainties in the raw counts and their ratio to local samples might
amount to as much as a factor of two.
  Within that uncertainty, the number density of red E/S0s to z = 0.8 seems
relatively static, being comparable to or perhaps moderately less than that of
local E/S0s depending on the assumed cosmology. A doubling of E/S0 number
density since z = 1 can be ruled out with high confidence (97%) if
\Omega_{m}=1.
  Taken together, our results are consistent with the hypothesis that the
majority of luminous field E/S0s were already in place by z = 1, that the bulk
of their stars were already fairly old, and that their number density has not
changed by large amounts since then.
