SYDNEY—No worries, mate: Australia may be the world's happiest industrialized nation by one reckoning, even as it grapples with rising inflation, pricey housing and worries that it is developing a two-track economy.

The resource-rich nation ranked highly in areas such as overall satisfaction, health, leisure time and community networks, according to a new survey released Wednesday by the Organization for Economic Cooperation and Development of the 34 nations that make up its membership. The index found that 75% of Australians...