Applications to American M.B.A. programs dropped for a fourth straight year, with even elite universities starting to show signs of struggling to lure young professionals out of the strong job market.

For the first time in nearly a decade, waning interest in the traditional master of business administration degree hit business schools that draw the most applications, including Harvard and Stanford universities, according to a survey of 360 schools by the Graduate Management Admission Council, a nonprofit that administers the GMAT admissions exam. Those top-tier programs were until recently thought to be immune to the shakeout plaguing less-prestigious programs.

Americans are saddled with more college debt than ever, and they have grown increasingly reluctant to leave behind jobs for a year or more to pursue one of the nation’s most expensive degrees, school administrators say—particularly as the economy has improved. In response, schools in recent years have launched cheaper, more flexible or more customized master’s degrees in hot areas such as data science and supply-chain management.

In the application year ended this spring, U.S. business schools received 140,860 applications for programs including the traditional two-year M.B.A., down 7% from the previous year, GMAC data shows.

Until recently, international students had been a bright spot for U.S. business schools. Now, foreign students face steeper hurdles to getting work visas after graduation, leading fewer to apply to U.S. schools, university administrators say.