Share of doublets at the 3σ (confidence level of 99.7%) vs. resolution for r < 24 doublets at z = 1 for different flux bins and with a flux ratio between the lines of 1. Each line corresponds to a survey with a the flux detection limit given on the right end of each line in units of 10^-17  erg   cm^-2   s^-1. SDSS-IV/eBOSS corresponds to line 30 and DESi to line 10.