R_A as a function of the redshift. Green circles depict the secure lens candidates (Foëx et al. 2013), and green diamonds those with 2.0′′ ≤ R_A ≤ 8.0′′. Blue asterisks with error bars highlight the correlation between R_A and z after binning the data (green diamonds). The blue continuous line shows the fit to the binned data, with 1σ-error depicted as a dotted blue line. The green continuous line shows the fit to the green diamonds, with the 1σ-error depicted as a gray shaded region. The dashed line is a second-order polynomial function from Zitrin et al. (2012), assuming an error of 15% (dot-dashed line).