"In CBO projections, deaths exceed births beginning in 2040," Swagel said during a discussion at the American Enterprise Institute.
As a result of this process, the US population would shrink thereafter without a "support" of immigration, Swagel said.
Swagel also said that higher-than-expected migration became the major driver of the labor force in the United States.
The CBO has increased its projection of the size of the labor market in 2033 by 5.2 million people from last year, Swagel added.