  We investigate six operations on chemical reaction networks, all of which
have been proven to preserve important dynamical properties, namely, the
capacity for nondegenerate multistationarity (multiple steady states) and
periodic orbits. Both multistationarity and periodic orbits are properties that
are known to be precluded when the deficiency (a nonnegative integer associated
to a network) is zero. It is therefore natural to conjecture that the
deficiency never decreases when any of the six aforementioned network
operations are performed. We prove that this is indeed the case, and moreover,
we characterize the numerical difference in deficiency after performing each
network operation.
