A lot of that depends on a couple of things:
* How good your data is to begin with.
* How good your data import person is and how much time they took to get things right.
Rarely has database corruption been a culprit for me.
The person importing the data can do things like look for duplicates, provide reports on missing dates of birth, addresses, etc. Of course, I am assuming the person doing the import is using a comprehensive tool like MS Access and not just using some automated import tool like the one that comes with AC.
JamesNT