Do Lensing Statistics Rule Out a Cosmological Constant?

We present new calculations of gravitational lensing statistics in view of recent revisions in our knowledge of the luminosity function and internal velocity dispersion of E/S0 galaxies that work as effective lenses for background high-redshift QSOs. We show that the theoretical prediction of the lensing statistics is much smaller than previously expected. In sharp contrast to earlier statistics supporting an Ω₀ = 1 universe, the small lensing probability reported from the Hubble Space Telescope (HST) Snapshot Lens Survey is in best agreement with a low-density, flat universe with Ω₀ ~= 0.2 and Ω₀ + λ₀ = 1. The age of this universe, combined with the HST measurement of a high value for the Hubble constant H₀, can be reconciled with the age of the oldest globular clusters in the Milky Way.