RNZ reports the high cost of living means many people struggle to meet basic needs.
The ADB points out that there is also a lack of access to basic infrastructure, services and utilities and low levels of employment or income generating opportunities.
Of 14 Pacific countries the Marshall Islands population is the most poor, with just over half its people living below the national poverty line.
Tonga's closest neighbours, Fiji, has 31% of its population living below the poverty line and Samoa 26.9%.
Vanuatu has the lowest poverty statistics at 12.7%.