American Idol, the program that launched the careers of singers Kelly Clarkson and Carrie Underwood, will take its final curtain call after its next season, Fox announced Monday.

“Nothing is forever in TV land,” says Sam Craig, a professor at New York University. After 15 seasons spanning 13 years, he says this is an “inexorable movement.”

Idol’s audience is now less than a third the size it was at its peak in 2006. But at nine million viewers per episode, it’s still significant, says Max Dawson, the director of national television and video research at Frank N. Magid Associates.

“That still makes Idol one of the top two or three rated programs on Wednesday nights,” he says. “The problem is this: it’s probably one of the most expensive programs on Wednesday night.”

In the beginning, Dawson says Idol was relatively cheap to make, but it’s become increasing expensive as its host and judges have commanded higher salaries. 

The 15-season run of “American Idol” inspired a number of reality TV shows with a panel of snarky judges — some of which will now outlast the program: