Gross National Happiness?

The tiny, Himalayan Kingdom of Bhutan is advocating a happiness measure based on issues such as care of the environment (http://www.grossnationalhappiness.com/). I can see the approach being useful in a small, relatively homogeneous community that largely makes its way by carefully controlled ecotourism but suspect that the approach would be more difficult in much larger, diverse countries where there likely to be much more variation in what people want (or think they want) to engender happiness. Some of Bhutan's thinking (albeit less defined) does seem to 'spill across' its border into neighbouring Sikkim.