For example, Frey and Stutzer (2002) noted that gains in subjective well-being level off once GDP per capita tops US$ 10,000, and Diener and Biswas-Diener (2002) found that the correlation between income and subjective well-being is far smaller in more developed countries. Diener and Suh (1999) observed a correlation of 0.62 between mean purchasing power12 and life satisfaction in the countries under review. But they did note outliers like Japan (high income and low subjective well-being) and poor countries whose population did not report extremely low satisfaction levels.