Redshift evolution of the neutral and molecular density parameters for the HM background setup, having wind velocity of 350 km/s, wind delay time of 0.025 Hubble time and a Salpeter IMF (black solid lines, HM). Results obtained by increasing, the wind velocity to 700 km/s (pink dotted lines, HM-w700), the wind delay time to 0.1 Hubble time (pink dashed lines, HM-wf) and by adopting a Chabrier IMF (green dot-dashed lines, HM-Chabrier) or a Chabrier IMF with unitary SN efficiency (green dot-dot-dot-dashed lines, HM-1-Chabrier) are shown, too.