But if parents are worried about the imbalance, they can simply make a concerted effort to spend more quality time with their younger children, he said.

Price's study follows findings by UCLA economist Sandra Black. She and two colleagues found that older siblings get more education and make more money than their younger brothers and sisters. Follow-up research connected birth order to IQ, but none of the studies answered why birth order had such an impact.

"Joe's work has taken a big first step in helping us understand what is driving these birth order differences," said Black, in a written statement. She is a co-editor of the Journal of Human Resources.

"It's among the first to use a large data set to document systematic differences in parental investments by birth order," Black said.

Price added he has a theory, which he hasn't been able to prove, regarding large families. He believes parents of large families have a "bigger pie" and manage to put in a lot of quality time with all their children, foregoing personal time-consuming practices. However, the oldest child still gets a bigger slice of that pie, he said.

Price received his doctorate in economics from Cornell University in August 2007 and earned his bachelor of arts in economics from BYU in August 2003.

Price is the first-born of five children. His second-born brother, who was in graduate school at Cornell the same time as Price, refutes his brother's findings, as well as other birth-order studies that state older kids are smarter, laughs Price.

---

E-mail: astewart@desnews.com