Estimates of the contribution of sample (cosmic) variance to the statistical uncertainty of the GSMF measurements. For each redshift bin, the upper panels show the GSMF 1/V_max measurements obtained from five VIPERS subregions of 2  deg², located respectively in the W1 field (three regions, blue diamonds, circles, and squares) and in the W4 field (two regions, red triangles, and downward triangles). The Schechter fit to the global GSMF of Fig. 5 is shown as reference (black solid line). The lower panels show the standard deviations estimated in each redshift bin from these five measurements (purple squares, Eq. (3)), together with the estimates of σ_cv obtained from 57 SHMR mocks by means of Eq. (2) (green crosses). To highlight how the effect of cosmic variance decreases at higher z, we report σ_cv,SHMR of the first redshift bin in the other panels (green dashed lines). In addition, the sample variance measured in 50 SAM mocks (grey solid line) and the estimates provided by Moster et al. (2011) method (black triangles) are shown as reference.