Hadronic contributions to electroweak parameter shifts

Usinge ⁺ e ^?-data, an updated analysis of hadronic contributions to electroweak parameter renormalizations is presented. We emphasize the estimate of uncertainties which is important for precision tests at LEP and SLC. ForM _z =93 GeV and sin² Θ ₀=0.22 hadronic contributions from 5 flavors are found to be $$\Delta r_{had}^{(5)} = 0.0326 \pm 0.0007(\Delta r_{QED,had}^{(5)} = 0.0286 \pm 0.0007)$$ and $$\Delta g_{had}^{(5)} = 0.0602 \pm 0.0016(\Delta g_{3\gamma ,had}^{(5)} = 0.0619 \pm 0.0016)$$ for the renormalization of α and α _g =α/sin² Θ ₀, respectively. Parameter shifts are calculated and uncertainties due to higher order effects are estimated.