A simple switch to PR won't prevent gerrymandering.  Ask the folks in
Ireland.

Mark E. Rush

A switch to PR would prevent gerrymandering, if you choose a form of PR in
which the whole territory is one single district (but PR produces many new
problems).

If you choose the form of PR with multiple districts, gerrymandering is
possible.
Although partisan gerrymandering is not a big issue in countries with PR
(except for Ireland and other few countries, which use STV and other forms
of single-member-disctrict-sistems), mallaportionment is a bigger problem.
Usually districts have 10- or even 20-members. In case country uses
20-member districts, a deviation of 10% is quite a large deviation (it means
that voters in smaller district get 2 representatives more than same number
of voters in lager district). And in most cases these countries' courts,
relying on German deviation of 33%, French deviation of 20%, and British
deviation of 50%, do allow such large differencies among district population
(they are missing that Germany, France and Britain use single-member
districts and that these differencies were allowed for island districts and
similar exceptional cases).

On my opinion 20% deviation in multimember districts is even worse than 20%
in singlemember districts. If a country is divided into two districts
containing half of the population each, and one has 18 representatives and
the other one 22, this mallaportions the whole half of the country and
"steals" two representatives from the district. It gives one district four
representatives more than the other, although both districts should get
equal number of them.

Since I am not acquainted with US practice, is there a difference between
deviation allowed for single- and multy-member districts in US local
elections? Are there any decisions on this issue?

Thanks,
Jurij

ps. An interesting form of gerrymandering was occuring in Kosovo for about a
decade. Kosovo was a Serbian region, but it contained only about 5% of
Serbian population (the rest were Albanians). Albanians refused to vote
since 1988, since they did not consider themselves citizens of Serbia.
Because Kosovo Serbs were mostly voters of governing party (led by Slobodan
Milosevic), this party drew districts in the way that Albanians were
considered voters when districts were drawn. This way Milosevic's party got
about 20 times more seats from Kosovo region than it would if Albanians, who
never voted anyways, were not considered as voters when the district lines
were drawn.