A back envelope calculation shows that the relative transverse beam size growh
rate ($1/\sigma_x \, d\sigma_x/dt$) is about 2.8\% per hour, for protons, at
980, during good stores. Meanwhile, the lummisosity lifetime of the store is
about 9 to 10 hours. When the collider runs optimally, this lifetime can be
explained based on the anticipated loss of pbar and protons due to collision
and emittance growths. It is shown that Intra Beam Scattering (IBS) is a significant
source of this emittance growth. Predictions from the IBS model are compared
with data. The predictions is in quantitative agreement with
observation. Large uncertainties are due to initial measurement errors, and, we
suspect, due to the fact that significant beam losses occurs at large
(longitudinal and/or transverse) amplitudes.