Men who belonged to unions their entire career made up to $1.3 million more on average than men who never joined one, according to new research.

Those belonging to unions made about $3.4 million from ages 20 to 64, compared to $2.1 million for those who were never union members. Cornell University's Industrial and Labor Relations (ILR) Review published the findings.

The study analyzed data from the Panel Study of Income Dynamics (PSID) from 1969 through 2019. The men studied had to be no older than 25 between 1969 and 1973.

The sample consists only of men because women earners are categorized as "spouse" in the PSID, and data on spouses only began being collected consistently in 1979, the researchers said.

Researchers calculated career earnings using total years employed, mean hours worked per year, and the mean hourly wage.

Men with no college degree who have been in a union at least half their career had expected earnings of $1.96 million by age 65, while those with no college degree who have never been in a union or been in one less than half of their career have projected earnings of about $1.5 million.

Inversely, people with college degrees who have been in a union for more than half their careers made less ($2.16 million) than those with college degrees who have never been in a union ($2.67 million), "likely because of the association of union membership and occupations worked," the study says.

Though, across the board, belonging to a union was associated with an increased probability of retiring at or before age 65.

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