In America, on the West coast, unions negotiate a common contract:
Ironically, the International Longshore and Warehouse Union is a
beneficiary of the same forces that are killing unions everywhere
else: Its workers are the folks who unload the stuff that comes in
from abroad. Those workers are sitting right at the bottleneck through
which all that foreign competition flows to the U.S., and due to some
smart planning by the union in earlier decades -- such as insisting
that the West Coast ports would bargain as a bloc so that they can't
play different locals against each other -- they can cork that
bottle anytime they want. That gives them the ability to extract a
little tariff on all that trade. Their rake-off is a tiny fraction of
the overall flows, but that still translates into substantial sums for
the few thousand workers who are holding onto that cork. The more
trade, the better the concessions the ILWU is able to extract -- and
the worse workers in other unions do.
Where Have All Our Wages Gone? by Megan Mcardle
There used to be a pre-anti-trust era railroad cartel in the USA:
The [Joint Executive Committee (JEC)] was a cartel formed by the
railroads which controlled eastbound freight shipments from Chicago to
the Atlantic seaboard in the I 88os. The agreement was publicly
acknowledged, as it preceded the passage of the Sherman Act (1890)
and the formation of the Interstate Commerce Commission (1887). ...
The JEC cartel agreement took the form of market share allotments
rather than absolute amounts of quantity shipped. Firms set their
rates individually, and the JEC office took weekly accounts so that
each railroad could see the total amount transported. Total demand was
quite variable, and the actual market share of any particular firm
depended on both the prices charged by all the firms and unpredictable
stochastic forces.
On the Incidence and Duration of Price Wars (Porter (1985))