Black points show the normalized fractions of binaries, ν_bin measured in five mass-ratio intervals as a function of q for all the GCs studied in this paper. To compare the fraction of binaries in different clusters we divided ν_bin by two times the fraction of binaries with q > 0.5. For clarity, black points have been randomly scattered around the corresponding q value. Red points with error bars are the means in each mass-ratio bin, while the gray line is the best fitting line, whose slope is quoted in the inset.