  We examine in this work the role of disorder in contributing to the sluggish
relaxation observed in intrinsic electron-glasses. Our approach is guided by
several empirical observations: First and foremost, Anderson localization is a
pre-requisite for observing these nonequilibrium phenomena. Secondly, sluggish
relaxation appears to favor Anderson-insulators with relatively large
Fermi-energies (hence proportionally large disorder). These observations
motivated us to consider a way to measure the underlying disorder in a
realistic Anderson insulator. Optical study using a series of amorphous
indium-oxide (In_{x}O) establish a simple connection between
carrier-concentration and the disorder necessary to approach the
metal-insulator transition from the insulating side. This is used to estimate
the typical magnitude of the quenched potential-fluctuation in the
electron-glass phase of this system. The implications of our findings on the
slow dynamics of Anderson-insulators are discussed. In particular, the reason
for the absence of a memory-dip and the accompanying electron-glass effects in
lightly-doped semiconductors emerges as a natural consequence of their weak
disorder.
