Reconstruction of the expansion rate, H(z)/(1 + z), as a function of the redshift using the combination of SNIa, BAO, and CMB data. In the top panel the data sets have been combined considering r_d a free parameter, while in the central panel a prior on r_d has been used, and it has been explicitly computed in the bottom panel. In all panels the black and gray lines represent the ΛCDM model (without and with SNIa luminosity evolution, respectively), while the red band shows the reconstruction with Δχ² ≤ 1 with respect to the best reconstruction (red line). The green band stands for the reconstruction of a coasting universe at low redshift when SNIa intrinsic luminosity is allowed to vary as a function of redshift. See the text for the details of the reconstruction.