Evolution of lithium compared to the prediction by Big Bang Nucleosynthesis (BBNS) given by the dotted line. The diamonds represent the observed Li abundances with their corresponding measurement error bars. The arrows represent upper limits. The square shows the Li-rich subgiant. Overplotted are predictions from stellar structure models including atomic diffusion and different efficiencies of AddMix. The initial abundance and corresponding uncertainty on the derived Li abundance are given by the dashed line and the shaded region, respectively. They have been adjusted so that predictions match the observed abundance level at the cool end of the T_eff scale. The shaded region around the dotted line gives the uncertainty interval of the Planck-calibrated primordial lithium abundance.