  Measurements of the cosmic ray pbar/p ratio are compared to predictions from
an inhomogeneous leaky box model of Galactic secondary pbar production combined
with an updated heliospheric model that modulates the predicted fluxes measured
at the Earth. The heliospheric corrections are crucial for understanding the
low-energy part of the spectrum. The pbar production- propagation-modulation
model agrees with observations. Adding a finite pbar lifetime to the model, we
obtain the limit tau(pbar) > 1.7 Myr (90% C.L.). Restrictions on heliospheric
properties and the cutoff of low-energy interstellar cosmic rays are discussed.
