[EM] Proportional Representation Systems I'd Support

[Kathy Dopp]

Upon cursory reflection and in response to my strong opposition to any
nonmonotonic method and to any method that fail to treat all voters'
votes equally, the only proportional method I know I would support for
legislative representation would be the party list system where
candidates appear only on one list, where parties can cross-endorse
another party's list instead of presenting their own list for any
particular contest. But I don't know how fractional left-over vote
shares are handled when this system fails to initially elect all the
seats with the required vote share per seat.  Is that when two or more
parties join forces to elect the rest of the seats and haggle over who
fills them?

Are there any other proportional methods besides the party list system
that are monotonic and treat all voters' votes equally (unlike IRV and
STV where some voters' votes rankings are counted when it would matter
and some are not)?

Kathy