Why Firstborns Earn More – And How Illness Plays a Role

According to a recent study, firstborn children tend to earn more than their younger siblings, and childhood health differences may explain about half of this income gap. Researchers analyzing data from individuals born in Denmark between 1981 and 2017 found that younger siblings were two to three times more likely to be hospitalized for respiratory conditions during their first year of life compared to their older brothers and sisters. These early-life health disparities may impact brain development and later mental health, potentially affecting long-term earning potential. Additional research supports the trend of firstborns achieving greater academic and economic success. A 2007 study of Norwegian men revealed an average IQ difference of approximately three points between first- and second-born children, translating to roughly a 2% difference in annual income. A 2011 Career Builder survey of U.S. Adults indicated that eldest children are most likely to attain six-figure salaries. Experts suggest several factors may contribute to these outcomes, including differences in parental investment. A 2017 Swedish study found that later-born children spend nearly an hour less per week on homework, are less inclined to read books, and spend more time watching television or using computers compared to their older siblings. These patterns may reflect shifting parental attention and resources as family size increases.