Left: estimates of the monopole of the redshift-space power spectrum from the four independent VIPERS subsamples in W1 and W4 and two redshift bins. The shaded area gives the diagonal error corridor around the 0.6 <z < 0.9 W1 sample, as provided by the dispersion of the corresponding mock catalogues. Right: corresponding likelihood surfaces for the simultaneous fit to the four power spectra. The contours correspond to two-parameter confidence levels of 68, 95 and 99 per cent. The measurements have been used down to scales corresponding to k_max = 0.40 h Mpc^-1 and we have marginalised over the galaxy bias and velocity dispersion.