  We present a robust method to constrain average galaxy star formation rates,
star formation histories, and the intracluster light as a function of halo
mass. Our results are consistent with observed galaxy stellar mass functions,
specific star formation rates, and cosmic star formation rates from z=0 to z=8.
We consider the effects of a wide range of uncertainties on our results,
including those affecting stellar masses, star formation rates, and the halo
mass function at the heart of our analysis. As they are relevant to our method,
we also present new calibrations of the dark matter halo mass function, halo
mass accretion histories, and halo-subhalo merger rates out to z=8. We also
provide new compilations of cosmic and specific star formation rates; more
recent measurements are now consistent with the buildup of the cosmic stellar
mass density at all redshifts. Implications of our work include: halos near
10^12 Msun are the most efficient at forming stars at all redshifts, the baryon
conversion efficiency of massive halos drops markedly after z ~ 2.5 (consistent
with theories of cold-mode accretion), the ICL for massive galaxies is expected
to be significant out to at least z ~ 1-1.5, and dwarf galaxies at low
redshifts have higher stellar mass to halo mass ratios than previous
expectations and form later than in most theoretical models. Finally, we
provide new fitting formulae for star formation histories that are more
accurate than the standard declining tau model. Our approach places a wide
variety of observations relating to the star formation history of galaxies into
a self-consistent framework based on the modern understanding of structure
formation in LCDM. Constraints on the stellar mass-halo mass relationship and
star formation rates are available for download at
http://www.peterbehroozi.com/data.html .
