[P]sychological evidence suggests that is is close relationships, a meaningful life, economic security, and health that contribute most to well-being. While there are marked improvements in happiness when people at low levels of income earn more (as their economic security improves and their range of opportunities grows), as incomes increase this extra earning power converts less effectively into increased happiness. In part, this may stem from people’s tendency to habituate to the consumption level they are exposed to. Goods that were once perceived as luxuries can over time be seen as entitlements or event necessities.
By the 1960s, for instance, the Japanese already viewed a fan, a washingmachine, and electric rice cookers as essential goods for a satisfactory living standard. In due course, a car, an air conditioner, and a color television were added to the list of “essentials.” And in the United States, 83 percent of people saw clothes dryers as a necessity in 2006. Even products around only a short time quickly become viewed as necessities. Half of Americans now think they must have a mobile phone, and one third of them see a high-speed Internet connection as essential.
Emphasis mine. From the State of the World 2010: Transforming Cultures. They also have a nice, WordPress-powered blog. (A necessity.) You can see the context of the quote in Google Books.