The Economist article actually conflates two happiness metrics, happiness as measured by emotional well-being and happiness as measured by life evaluation. Money buys happiness as measured by emotional well-being up to a point (that point being $75K for US residents), but higher income continues to increase life evaluation.<p>More details can be found in Daniel Kahneman's 2010 study, "High income improves evaluation of life but not emotional well-being"(<a href="http://www.pnas.org/content/107/38/16489.full" rel="nofollow">http://www.pnas.org/content/107/38/16489.full</a>), where he uses the results of 450,000 Gallup poll responses to analyze the effects of income on both happiness metrics.<p>Kahneman defines emotional well-being as "the emotional quality of an individual's everyday experience—the frequency and intensity of experiences of joy, stress, sadness, anger, and affection that make one's life pleasant or unpleasant." Life evaluation, on the other hand, refers to the thoughts that people have about their life when they think about it."<p>In the study, emotional well-being is captured via series of yes/no questions of the form "Did you experience a lot of stress yesterday?" or "Did you smile or laugh a lot yesterday?" The goal is to assess their emotional well-being on the previous day. Life evaluation is measured by asking respondents to rate their lives on a ladder scale from 0-10, where 0 is “the worst possible life for you” and 10 is “the best possible life for you.”<p>The data showed that for individuals earning below $75K, logarithmic increases in income (i.e. doubling one's income) positively correlate with scores for happiness, enjoyment, and smiling and negatively correlate with scores for sadness, worry, and stress. At $75K, you have enough to pay life's bills and still have discretionary money to go out and spend time with friends. The effects of income on emotional measures saturate at $75K because money no longer becomes the limiting resource for achieving more happiness, even though life satisfaction continues to rise when plotted against log income. "We conclude that high income buys life satisfaction but not happiness, and that low income is associated both with low life evaluation and low emotional well-being," Kahneman writes.