We examine the global stability of an exponential stellar disk embedded in a dark matter halo and constrain the mass-to-light ratio of observed disks in the I-band, ΥI . Assuming only that the radial surface density distribution of disks is exponential, we derive an analytic upper limit: ΥI ∼ 2.4h, for a Hubble constant of 100h km s Mpc. Using N -body… (More)