Bill,
If you are referring to Custom Attribute, in Liferay 5.2.3, then I believe this is a normal behavior.
You can take a look at the "expandovalue" table and see how many users have values for the Custom Attribute (map classPK with userId).
It would have been great to assign default value to exiting users once a Custom Attribute is created. You probably have to write your own process to do that.
Ali
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