“unexpected” unfunded liabilities are very very sneaky. You never know where they’ll show up next.
He has been seen as a curmudgeon but thankfully has had a larger audience inside Germany than his research collaborators have had, ( in the US, Canada, Chile, Austria and other locales), though his collaborator in Chile is partially responsible for the privatization drive of the Chilean equivalent of US Social Security.
For a super wonkish view check Google Scholar search results: