STATUS OF PERTURBATIVE QCD EVALUATION OF HADRONIC DECAY RATES OF THE Z AND HIGGS BOSONS

We review the current status of the high order perturbative QCD evaluation of the hadronic decay rates of the Z and Higgs bosons. A systematic classification of the various types of QCD corrections to $O({\alpha }_s^2)$ and $O({\alpha }_s^3)$ is made and their numerical status is clarified.