that some regions have in recent years been experiencing progressive inequality of happiness. Other measures The Physical Quality of Life Index (PQLI) is a measure developed by sociologist M. D. Morris in the 1970s, based on basic literacy, infant mortality, and life expectancy. Although not as complex as other measures, and now essentially replaced by the Human Development Index, the PQLI is notable for Morris's attempt to show a "less fatalistic pessimistic picture" by focusing on three areas where global quality of life was generally improving at the time, while ignoring gross national product and other possible indicators that were not improving. The Happy Planet Index, introduced in 2006, is unique among quality of life measures in that, in addition to standard determinants of well-being, it uses each country's ecological footprint as an indicator. As a result, European and North American nations do not dominate this measure. The 2012 list is instead topped by Costa Rica, Vietnam and Colombia. In 2010, Gallup researchers trying to find the world's happiest countries found Denmark to be at the top of the list. For the period 2014–2016, Norway surpasses Denmark to be at the top of the list. uSwitch publishes an annual quality of life index for European countries. France topped the list from 2009 to 2011. A 2010 study by two Princeton University professors looked at 1,000 randomly selected U.S. residents over an extended period. It concludes that their life evaluations – that is, their considered evaluations of their life against a stated scale of one to ten – rise steadily with income. On the other hand, their reported quality of emotional daily experiences (their reported experiences of joy, affection, stress, sadness, or anger) levels off after a certain income level (approximately $75,000 per year in 2010); income above $75,000 does not lead to more experiences of happiness nor to further relief of unhappiness or stress. Below this income level, respondents reported decreasing happiness and increasing sadness and stress, implying the pain of life's misfortunes, including disease, divorce, and being alone, is exacerbated by poverty. Gross national happiness and other subjective measures of happiness are being used by the governments of Bhutan and the United Kingdom. The World Happiness report, issued by Columbia University is a meta-analysis of happiness globally and provides an overview of countries and grassroots activists using GNH. The OECD issued a guide for the use of subjective well-being