  A conventional approach to precision calculations of Higgs boson observables
uses quark masses $m_c$ and $m_b$ as inputs. However, quark masses are single
numbers that hide a variety of low-energy data from which they are extracted,
and also hide the various sources of theoretical uncertainties and correlations
with additional input parameters such as $\alpha_s$. Higher-precision
calculations, which are needed to give meaning to future measurements, require
more direct engagement with the low-energy data in a global analysis. We
present an initial calculation in this direction, which illustrates the
procedure and reveals some of the theory uncertainties that challenge
subpercent determinations of Higgs boson partial widths.
