Evolution of the fraction of IR luminosity due to the LIRGs in groups (black points) and in the total IR galaxy population (red shaded region). This is obtained as the ratio between the integral of the observed IR LF down to L_IR> 10¹¹ L_⊙ and the integral estimated down to L_IR> 10⁷ L_⊙ of the group and total IR LF, respectively. The red shaded region is obtained by considering in any redshift bin the whole range of possible values, including errors, derived from the total IR LF estimated by Sanders et al. (2003), Le Floc’h et al. (2005), Rodighiero et al. (2010), Magnelli et al. (2009, 2011, 2013), Gruppioni et al. (2013).