I have been enjoying this discussion of the proposed policy, and intend to
weigh in with my own overwrought opinion before the deadline.  I thought
some numbers might be of interest.

The most recent LC names weekly file processed here (lcname05.25) contains
8830 authority records, of which 5642 represent simple personal name
headings (tag 100; subfield $t is not present).  Of those 5642 simple
personal name headings:
        New record, subfield $d code not present: 2670
        New record, subfield $d code present: 979
        Delete record, subfield $d code not present: 52
        Delete record, subfield $d code present: 18
        Replacement record, subfield $d code not present in incoming heading: 1279
        Replacement record, subfield $d code present in incoming heading: 644

The previous version of the heading in 29 of the 644 replacement records
did not contain the subfield $d code: these 29 records appear to have been
changed to add a date.  Of these 29 headings, in 3 cases the earlier
headings actually contained dates, but mistakenly lacked the subfield $d
code itself; in 3 other cases headings were changed in other ways at the
same time the date was added. Of the 23 personal name headings in this file
that differ only in the addition of subfield $d and dates, a strict
definition of what constitutes a "conflict" (and searching only in the
authority file itself) leads me to label 6 headings as having been changed
as the result of a conflict, and 17 to have been changed in the absence of
a conflict. Here are two examples of each:

        n 79044092: Jensen, Eric, $d 1950-
        Date added to existing heading to make way for new heading without date

        n 84113305: Murphy, Peter E., $d 1942-
        Date added to existing heading to make way for new heading without date

        no 2005007464: Manistina, Elena, $d 1973-
        Date added to non-conflicting heading

        no 2005053962: Wallace, Patricia H., $d 1947-
        Date added to non-conflicting heading

Although numbers are small, there does appear to be at least one
sub-category of headings that might be recognized among the 17 headings
changed without evidence of conflict. The reconstruction of events for
these might be one of the following: 1) the institution that established
the heading missed a date of birth that appeared somewhere in the
publication, the date was found by another institution handling the same
item and the second institution changed the 670 and the heading; 2) the
heading was established from CIP information, a date of birth arrived with
the full publication and the 670 and heading were changed. I do not believe
that any such are included in the above examples.

I searched a 10% sample of the 979 new records for simple personal names
with $d (97 headings examined), in the authority file. Using a looser
definition of conflict than used above for changed headings (allowing the
addition of dates to a new heading if not strictly required to break a
conflict, when similar headings exist), I determined that 21 of the
headings (22%) contained $d because it was needed to break a conflict or
made a set of headings easier to understand; and 76 (78%) contained $d
because it was available but was not required or particularly useful.  Here
are two examples of each:

        n 2005043497: Feenie, Rob, $d 1965-
        No other 'Feenie, Rob' in authority file

        n 2005043541: Sikora, Ruzhena, $d 1918-
        No other 'Sikora, Ruzhena' in authority file

        n 2005044002: Rosen, David, $d 1971-
        Date required: 'Rosen, David' with no date already established

        n 2005044208: Coleman, Brian, $d 1970-
        Date required: 'Coleman, David' with no date already established

Gary L. Strawn, Authorities Librarian, etc.
Northwestern University, 1970 Campus Drive, Evanston IL 60208-2300
e-mail: [log in to unmask]   voice: 847/491-2788   fax: 847/491-8306
Forsan et haec olim meminisse iuvabit.