  The LASCO coronagraphs, in continuous operation since 1995, have observed the
evolution of the solar corona and coronal mass ejections (CMEs) over a full
solar cycle with high quality images and regular cadence. This is the first
time that such a dataset becomes available and constitutes a unique resource
for the study of CMEs. In this paper, we present a comprehensive investigation
of the solar cycle dependence on the CME mass and energy over a full solar
cycle (1996-2009) including the first in-depth discussion of the mass and
energy analysis methods and their associated errors. Our analysis provides
several results worthy of further studies. It demonstrates the possible
existence of two event classes; 'normal' CMEs reaching constant mass for $>10$
R$_{\sun}$ and 'pseudo' CMEs which disappear in the C3 FOV. It shows that the
mass and energy properties of CME reach constant levels, and therefore should
be measured, only above $\sim 10 R_\sun$. The mass density ($g/R_\sun^2$) of
CMEs varies relatively little ($<$ order of magnitude) suggesting that the
majority of the mass originates from a small range in coronal heights. We find
a sudden reduction in the CME mass in mid-2003 which may be related to a change
in the electron content of the large scale corona and we uncover the presence
of a six-month periodicity in the ejected mass from 2003 onwards.

Solar and Stellar Astrophysics