Census figures show the population of Wallis and Futuna declined by 10% between 2003 - 2008 to just over 13,000 people.
Fertility has declined to two children per woman while the population has aged, with 11% of residents now over 60.
Radio New Zealand International reports the decline is attributed to continued emigration - mainly to New Caledonia, whose Wallisian population has risen to 25,000.
Education achievements are relatively low and economic development is limited. Only 28% of the population of Futuna is in paid employment compared to 63% across all of France and its territories.
Last year, assembly president Victor Brial warned that the population decline could spell the end of the archipelago's Polynesian culture.
