More than three-fourths of U.S. millennial workers who quit their job do so because of minimal wage growth, according to a new study by Ernst & Young in New York City. Nearly 9,700 full-time workers in eight nations participated in the online survey.

"Knowing that millennials and parents are under increasing pressure, we wanted to understand what employees seek in a job and why they quit, why they stay and how this differs by generation," said Karyn Twaronite, EY global diversity & inclusiveness officer.

The reasons why millennials quit vary from country to country. The top five reasons in the United States are:

• Minimal wage growth (78 percent)

• Lack of advancement opportunities (75 percent)

• Excessive overtime hours (72 percent)

• An environment that doesn't encourage teamwork (66 percent)

• A boss who doesn't allow flexibility (66 percent)

An employee's family situation is another important factor. Parents are more likely than non-parents to mention a lack of opportunity to advance as a reason to quit, which shows continued career ambition after having children. Parents also are more likely to emphasize flexibility issues.