The fraction of electrons that are successfully moved from one pixel to another during read-out is described by the charge transfer efficiency (CTE).
The CTE has been measured using a 
Fe X-ray source, whose emissions
generate a specific number of photo-electrons on the CCD for each detection.
The read-out counts as a function of position on the CCD can then be converted
to a CTE value.
The values found are:
Transporting the charge from the most remote corner of the CCD to the output amplifier will then lead to a 0.6% loss of charge
Note that CTE strictly speaking is a function of exposure level, so the value given here may not be applicable to all cases. Near zero level and full well, CTE can be expected to be poorer.