If everyone had the same income, the differences among people in life satisfaction would be reduced by less than 5%.

From 2011: WHAT SCIENTIFIC CONCEPT WOULD IMPROVE EVERYBODY'S COGNITIVE TOOLKIT?  Focusing Illusion by Daniel Kahneman.

Focusing Illusion 

 

"Nothing In Life Is As Important As You Think It Is, While You Are Thinking About It"

Education is an important determinant of income — one of the most important — but it is less important than most people think. If everyone had the same education, the inequality of income would be reduced by less than 10%. When you focus on education you neglect the myriad other factors that determine income. The differences of income among people who have the same education are huge.

Income is an important determinant of people's satisfaction with their lives, but it is far less important than most people think. If everyone had the same income, the differences among people in life satisfaction would be reduced by less than 5%.

Income is even less important as a determinant of emotional happiness. Winning the lottery is a happy event, but the elation does not last. On average, individuals with high income are in a better mood than people with lower income, but the difference is about 1/3 as large as most people expect. When you think of rich and poor people, your thoughts are inevitably focused on circumstances in which their income is important. But happiness depends on other factors more than it depends on income.

Paraplegics are often unhappy, but they are not unhappy all the time because they spend most of the time experiencing and thinking about other things than their disability. When we think of what it is like to be a paraplegic, or blind, or a lottery winner, or a resident of California we focus on the distinctive aspects of each of these conditions. The mismatch in the allocation of attention between thinking about a life condition and actually living it is the cause of the focusing illusion.