Do Firstborn Children Really Earn More? Science Says Yes!

Have you ever noticed that within a family, the eldest sibling often seems to have a natural knack for success and financial prosperity? Well, it seems like firstborn children do actually earn more!

While birth order psychology has long been a topic of intrigue, recent research has shed light on a new theory that could explain why oldest siblings tend to outshine the rest when it comes to their earning potential.

Study Shows That Firstborn Children Earn More

Researchers have discovered that eldest children often earn higher incomes and score better on cognitive tests than their younger siblings. However, experts remain divided on the main factors contributing to this trend.

A February working paper from the National Bureau of Economic Research found that a significant factor affecting younger siblings’ performance is their higher likelihood of being sick as infants.

The Study

Researchers analyzed data on siblings born in Denmark from 1981 to 2017. They found that younger siblings were two to three times more likely to be hospitalized for respiratory conditions in their first year. This disparity was most significant when the second child was born in the fall or winter. This is when respiratory illnesses were more prevalent, and when siblings were closer in age.

N. Meltem Daysal, an associate professor at the University of Copenhagen, explained that younger siblings may be more susceptible to illness because older siblings often bring home viruses from group childcare.

What Else Did They Discover?

The researchers found that exposure to illnesses may have lasting financial effects. This revealed that younger siblings in Denmark earned an average of 2.4% less than their older siblings when they entered the workforce. The results were based on data from children born between 1981 and 1989.

Daysal stated that younger siblings exposed to more viruses in infancy tend to have lower adult earnings. The researchers believe this is mainly due to severe respiratory illnesses in early life. These can impair brain development and subsequently impact mental health.

She explained: “Younger siblings with higher virus exposure in infancy have lower earnings as adults. We think that the primary mechanism explaining this result is that severe respiratory illness among very young babies can lead to the impairment of brain development, which, in turn, can affect later mental health.”

Health Is an Important Factor

Younger siblings in areas with higher rates of infant respiratory illness were more likely to seek mental health resources in young adulthood. Daysal noted that early health disparities accounted for about 50% of the earnings gap between younger and older siblings.

There Is Another Reason Why Firstborn Children Earn More

Dayal mentioned that studies from various countries support the finding that older siblings generally achieve higher levels of education and economic success compared to their younger siblings.

A 2007 study of Norwegian men found that first-born children had an average IQ advantage of about three points over second-born siblings. This led to a roughly 2% difference in annual earnings. Additionally, a 2011 Career Builder survey indicated that first-born children in the US were the most likely to earn six-figure salaries.

Sandra Black, an economics professor at Columbia University, stated in 2018 that first-born children generally perform better in education and earnings. She noted a declining pattern by birth order, with each subsequent sibling doing slightly worse than the one before.

Do Other Researchers Agree?

Some researchers challenge certain findings, such as a 2015 paper. It showed that the differences in IQ and personality among siblings are minimal. Additionally, the higher likelihood of respiratory illness among younger siblings is not the only explanation for the disparities in outcomes.

Some suggest that parents may become less invested in raising subsequent children after the firstborn. This could then negatively impact their development and future outcomes.

Other Studies Also Explain Their Opinions

A 2017 study of Swedish men found that later-born siblings spent nearly an hour less on homework each week than first-borns, were less likely to read books, and were more likely to watch TV or play on the computer. Parents also reported spending less time discussing schoolwork with their later-born children.

The authors suggested that their results indicate parents invest less in later-born children by being less strict and providing less supervision.

Are There Any Other Explanations Why Firstborn Children Earn More?

Another possible explanation is that first-borns benefit from helping their younger siblings. In his 2023 book “Hidden Potential,” organizational psychologist Adam Grant cited research showing that only children typically perform worse on cognitive tests than first-borns with younger siblings, which may be linked to a “tutor effect.”

Adam Grant noted that firstborns in large families learn by educating their younger siblings. These benefits typically begin to appear around age 12, when older siblings have more knowledge to share and younger siblings are more receptive to learning.

What About Biological Differences?

Some researchers argue that biological differences do not account for the disparities in outcomes among siblings. Grant referenced a study of 240,000 Norwegian teenagers, which found that younger siblings whose first-born siblings died in infancy scored higher in intelligence than later-born siblings.

This suggests that first-born advantages stem from nurture rather than nature, allowing researchers to rule out biological and prenatal causes.

Firstborn Children Are Also More Caring

First-born siblings often take on roles such as leaders, teachers, and caregivers, while second-born siblings tend to imitate, follow, and learn from their older siblings. Younger siblings frequently mimic the older child’s language and actions during play, establishing shared meanings.

Siblings can teach each other during structured tasks and play, considering each other’s knowledge. In early childhood, they can provide support during caretaking when parents are absent, and in middle childhood, they offer support during stressful family situations.

The age difference creates distinct family experiences, with second-borns benefiting from learning opportunities provided by their older siblings, sometimes leading to advanced development in certain areas.

What do you think? Do firstborn children in your family also earn more? Let us know about your experience in the comments below!

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