The interstellar medium depletion time, $\tau_\mathrm{H2}$, plotted against a quantity proportional to the Krumholz-McKee star formation efficiency, ($\sigma_v^{(-0.32)} (M/R^3)^{(0.5)}$), on a logarithmic scale. The small points are the nuclear clouds. The unfilled, large points are the arm clouds and the filled large points are the inter-arm clouds. The separation between the populations suggests that GMAs are different in the arm vs. inter-arm and they drive a change in the star formation efficiency in the rough direction expected by theory.  
\label{SFE}