  Two simple ways by which the standard signals of the Standard Model Higgs
boson can be depleted are: its couplings to fermions and gauge bosons can be
suppressed by a universal factor, and part of its branching fraction can be
drained into invisible final states. A large class of theories can impose one
or both of these depletion factors, even if mild, by way of additional scalar
bosons that are singlets under the Standard Model but mix with the Higgs boson.
We perform a comprehensive survey of the present status of the depleted Higgs
boson, and discuss future prospects for detecting the presence of either
depletion factor. We also survey the constraints status and future detection
prospects for the generic case of extra mixed-in scalars which generically lead
to these depletion factors for the Higgs boson. We find, for example, that
precision study of the Higgs boson in many cases is more powerful than searches
for the extra scalar states, given the slate of next-generation experiments
that are on the horizon.
