  The HectoMAP survey provides a complete, mass-limited sample of 30,231
quiescent galaxies with $i-$band Hyper Suprime-Cam Subaru Strategic Program
(HSC SSP) imaging that spans the redshift range $0.2 <z < 0.6$. We combine
half-light radii based on HSC SSP imaging with redshifts and D$_n4000$ to
explore the size - mass relation, $R_{e} = A \times M_{*}^{\alpha}$, and its
evolution for the entire HectoMAP quiescent population and for two subsets of
the data. Newcomers with $1.5 < \mathrm{D}_n4000 < 1.6$ at each redshift show a
steeper increase in $A$ as the universe ages than the population that descends
from galaxies that are already quiescent at the survey limit, $z \sim 0.6$ (the
resident population). In broad agreement with previous studies, evolution in
the size - mass relation both for the entire HectoMAP sample and for the
resident population (but not for the newcomers alone) is consistent with minor
merger driven growth. For the resident population, the evolution in the size -
mass relation is independent of the population age at $z \sim 0.6$. The
contrast between the sample of newcomers and the resident population provides
insight into the role of commonly termed "progenitor bias" on the evolution of
the size - mass relation.
