Subdivided LCSH headings should be flipped by Preferred Term Correction
Preferred Term Correction is not flipping all LCSH headings when the authority record changes. If there is an authority record that has a subdivision, it is only flipped by PTC if the heading in the bib has no additional subdivisions. This means there is a significant gap in the PTC process that requires manual attention and handling, which is unsustainable. The PTC process needs to be more thorough.
For example, this LCSH:
$a Germany $x Politics and government $y 19th century
was updated by LC to be:
$a Germany $x Politics and government $y 1789-1900
When the authority record changed, bib headings that had the original $a $x $y (only) were flipped by PTC to have the new $y. But any headings that had additional subdivisions were not flipped.
For example, this bib heading was flipped to the new form:
BEFORE: $a Germany $x Politics and government $y 19th century
AFTER: $a Germany $x Politics and government $y 1789-1900
But this bib heading was NOT flipped:
$a Germany $x Politics and government $y 19th century $v Congresses.
More example of headings that were not flipped but should have been flipped:
651 0 $a Germany $x Politics and government $y 19th century $v Caricatures and cartoons.
651 0 $a Germany $x Politics and government $y 19th century $v Congresses.
651 0 $a Germany $x Politics and government $y 19th century $v Exhibitions.
651 0 $a Germany $x Politics and government $y 19th century $x In literature.
651 0 $a Germany $x Politics and government $y 19th century $v Periodicals.
651 0 $a Germany $x Politics and government $y 19th century $v Poetry.
Impact of Problem: The fact that PTC does not flip these headings means that staff have to manually correct hundreds or thousands of headings. The PTC process is lacking and is not performing its function of managing authority control automatically.

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Lynne Billington commented
Great idea!