World Summary of $\alpha_s$ (2012)
  Determinations of the strong coupling strength, $\alpha_s$, are summarised and a new world average value of $\alpha_s (M_Z)$ is determined, using a new method of pre-averaging results within classes of measurements like hadronic $\tau$ decays, deep inelastic scattering processes, lattice calculations, electron-positron annihilation processes and electro-weak precision fits. The overall result is $$\alpha_s (M_Z) = 0.1184 \pm 0.0007,$$ unchanged from the value obtained in 2009. This presentation is an excerpt from the QCD review section of the 2012 Review of Particle Physics (RPP) of the Particle Data Group. 
Siegfried Bethke
hep-ex hep-ph