Left panel: star formation efficiency as a function of stellar mass surface density. The different classes of galaxies from S11 are represented by differently coloured filled squares. The typical errorbars for S11 data points are represented by the black error bars. FIGGS galaxies are represented by violet circles with errorbars. The solid and dotted lies are the best fit and 1σ scatter around the best fit from S11. Right panel: star formation efficiency as a function of gas surface density. All symbols are the same as in left panel. The solid and dotted lies are the best fit and 1σ scatter around the best fit from S11 which excludes early types and LSBs.