Fraction of binaries with q > 0.5 measured in three magnitude intervals (black points) as a function of Δm_F814W for the 59 GCs studied in this work. To compare the fraction of binaries in different clusters we have divided the fraction of binaries in each bin by the value of measured in the interval between 0.75 and 3.75 F814W magnitudes below the MS turn off. For clarity black points have been randomly scattered around the corresponding Δm_F814W value. Red points with error bars are the average binary fractions in each interval while the gray line is the best fitting least-square line whose slope is quoted in the inset.