  We calculate one loop $y_t$ and $\lambda$ dependent corrections to
$\bar{\Gamma}_Z,\bar{R}_f^0$ and the partial $Z$ widths due to dimension six
operators in the Standard Model Effective Field Theory (SMEFT), including
finite terms. We assume $\rm CP$ symmetry and a $\rm U(3)^5$ symmetry in the UV
matching onto the dimension six operators, dominantly broken by the Standard
Model Yukawa matrices. Corrections to these observables are predicted using the
input parameters $\{\hat{\alpha}_{ew}, \hat{M}_Z, \hat{G}_F, \hat{m}_t,
\hat{m}_h\}$ extracted with one loop corrections in the same limit. We show
that at one loop the number of SMEFT parameters contributing to the precise
LEPI pseudo-observables exceeds the number of measurements. As a result the
SMEFT parameters contributing to LEP data are formally unbounded when the size
of loop corrections are reached until other data is considered in a global
analysis. The size of these loop effects is generically a correction of order
$\sim\%$ to leading effects in the SMEFT, but we find multiple large numerical
coefficients in our calculation at this order. We use a $\rm \overline{MS}$
scheme, modified for the SMEFT, for renormalization. Some subtleties involving
novel evanescent scheme dependence present in this result are explained.

High Energy Physics - Phenomenology