The strong U.S. economy has created millions of jobs and pushed up wages for many Americans. It also helped many big-company CEOs secure another raise and total compensation worth $1 million a month.

Median compensation for 132 chief executives of S&P 500 companies reached $12.4 million in 2018, up from $11.7 million for the same group in 2017, according to a Wall Street Journal analysis. The gains were driven by robust corporate profits and strong stock market returns for much of the year.

Most...