The Ministry of Transport study has found a more than 10-fold increase in the volume of container movements on larger ships over the past two years, which now account for more than one-third of the traffic in and out of New Zealand.
In 2012, only 3 percent of container movements were on international container ships bigger than 4,000 TEUs (twenty foot equivalent units), compared to 35 percent this year.
The ministry's aviation and maritime general manager, Nick Brown, said the study highlighted the need to reduce domestic freight costs.
The ministry also said 99 percent of New Zealand's international freight is carried by sea, and this country's international sea freight costs are 21 percent higher than those of Australia.
