Using a compilation of 25 studies from the literature, we investigate the evolution of the star-forming galaxy (SFG) Main Sequence (MS) in stellar mass and star formation rate (SFR) out to $z sim 6$. After converting all observations to a common set
of calibrations, we find a remarkable consensus among MS observations ($sim 0.1$ dex 1$sigma$ interpublication scatter). By fitting for time evolution of the MS in bins of constant mass, we deconvolve the observed scatter about the MS within each observed redshift bins. After accounting for observed scatter between different SFR indicators, we find the width of the MS distribution is $sim 0.2$ dex and remains constant over cosmic time. Our best fits indicate the slope of the MS is likely time-dependent, with our best fit $logtextrm{SFR}(M_*,t) = left(0.84 pm 0.02 - 0.026 pm 0.003 times tright) log M_* - left(6.51 pm 0.24 - 0.11 pm 0.03 times tright)$, with $t$ the age of the Universe in Gyr. We use our fits to create empirical evolutionary tracks in order to constrain MS galaxy star formation histories (SFHs), finding that (1) the most accurate representations of MS SFHs are given by delayed-$tau$ models, (2) the decline in fractional stellar mass growth for a typical MS galaxy today is approximately linear for most of its lifetime, and (3) scatter about the MS can be generated by galaxies evolving along identical evolutionary tracks assuming an initial $1sigma$ spread in formation times of $sim 1.4$ Gyr.
