(USA TODAY) -- Television's singing competitions don't make stars like they used to.
More specifically, Fox's long-running American Idol (returning Wednesday, 8 ET/PT) doesn't, because the two more recent arrivals, NBC's The Voice and Fox's The X Factor, have yet to produce a breakout performer.
Not surprisingly, the two music superstars produced since Idol began - Kelly Clarkson and Carrie Underwood, who won in 2002 and 2005, respectively - have had the biggest musical impact, with each responsible for at least 13 million album sales and 28 million downloads, according to sales data provided by Nielsen SoundScan.
Idol's 2006 finalist Chris Daughtry is the next closest performer, with numbers roughly half that size, while Jennifer Hudson is a major star, but her rise was powered more from by her Oscar-winning performance in 2006's Dreamgirls. Clarkson, Underwood and Daughtry are also the top three in radio play, with Jordin Sparks (2007), Fantasia (2004) and Josh Gracin (2003) taking the next three spots in number of spins.
Since Daughtry, others have enjoyed success, including Idol's Phillip Phillips (2012), Scotty McCreery (2011), Adam Lambert (2009) and David Cook (2008), but none approached the sales numbers of the earlier stars.
The Voice has not produced any stars, as evidenced by low album sales for 2012 and 2013 winners Cassadee Pope (206,000) and Danielle Bradbery (134,000). The X Factor's first two winners, Melanie Amaro and Tate Stevens, might as well have gone into a witness-protection program, a marked contrast to the British version that launched One Direction, Cher Lloyd and Leona Lewis. And previous Idol winners such as Taylor Hicks and Ruben Studdard, and runner-up Katharine McPhee, haven't become recording stars.
"In terms of a general pop star, we haven't seen one of those come out of a (U.S.) show for a while now," says Richard Rushfield, author of American Idol: The Untold Story.
Many factors are at play, including the loss of novelty as Idol ages and the newer singing shows clogged the scene, the smaller audience of Idol viewers and the music industry's larger woes.
"The Search for a Superstar" has been part of Idol's title since its start in 2002, and the show gained credibility with the recording success of inaugural winner Clarkson and later champ Underwood.
Thanks to the pair, Idol thrived, rising as a cultural phenomenon and ratings monster, with more than 30 million viewers tuning in by Season 5, when Daughtry performed.
Idol had the field to itself until 2011, when NBC introduced The Voice and Fox added The X Factor, creating a glut of singing shows and aspiring stars. But Idol has suffered ratings drops of more than 20% in the past two seasons, falling from 25 million to 15 million viewers.
"The water-cooler nature of Idol has dissipated over time," Billboard senior correspondent Phil Gallo says. "Those records that at one point could sell a certain amount because they were a souvenir to fans, that doesn't happen anymore."
Recent Idol winners have enjoyed greater sales success than their contemporaries on The Voice, which returns Feb. 24, and The X Factor, whose future is uncertain. McCreery has found a niche in country music and Phillip Phillips had a huge hit with Home, his Idol coronation song, featured in Olympics coverage and commercials.
Home accounts for two-thirds of Phillips' download sales. "They made his song a hit. (But) I think the jury's still out on whether he's going to be a star or not," Rushfield says.
Idol judge Jennifer Lopez says Phillips is a star and shows Idol can still fulfill its mission. "This guy's going to be an artist for a long time," she says.
With Home, Phillips tapped into the key to recording success, Gallo says. "TV is extremely important for launching people, but the No. 1 driver is the song. These days, people are more likely to latch onto a song than a singer," he says.
Creating stars gave Idol credibility, but it's no longer clear that it's necessary for a singing competition's success. The Voice is thriving, surpassing Idol in young-adult viewers for the first time last year and winning an Emmy Award, even though it has not produced a recording star
"The only thing that jades me just a bit about The Voice is that we have yet to discover and unleash to the world the new, the next big thing and true star on the big stage, and I would like to be responsible for that," Voice coach CeeLo Green says.
Last summer, Voice coach Adam Levine and host Carson Daly said making stars isn't the show's main goal. "I think we all know that the lightning in a bottle you have to capture in order to be successful in this business is extraordinarily difficult," Levine said. "I'm not sure that is the overall mission statement of the show."
The X Factor, however, has struggled in the ratings, and Fox Entertainment chairman Kevin Reilly says a few stars could have helped.
"One of the challenges we had here is we didn't have those breakouts the way they did in the U.K., and that made a huge, huge difference," he says. For music competitions in general, making a star can provide "a certain resonance when you realize that it is real and this is not just a prize to someone who's going to go away tomorrow and never be seen."
In the digital age, unknowns now have alternative ways to find a large following, but Idol judge Keith Urban says the music show has "production values that you can't afford on YouTube, because it's not your bedroom. You're on stage with a full band."
Fellow judge Harry Connick Jr., says he remains optimistic the show can mint stars.
"Will Idol discover a Kelly Clarkson or a Jennifer Hudson or a Carrie Underwood or an Adam Lambert, somebody who's mega-level? Absolutely," he says. "I don't know if it's going to be this year. I would like to think so, based on the talent we've seen. But, oh my God, yes. This is the platform on which to make it happen."
The top 20 album sellers from recent reality TV singing competitions all hail from American Idol. The closest competitor from another show is Cassadee Pope, who won Season 3 of The Voice in 2012, with 206,000 album sales, a little more than half the total of Idol's No. 20, Kris Allen. Eight of the top 10 come from the first five of Idol's 12 seasons. Here is a list of the singers, the year they appeared on Idol and career sales.
The top 20 album sellers from recent reality TV singing competitions all hail from American Idol. The following chart lists singers, the year they appeared on Idol and their career sales.
Artist (Year on American Idol) | downloads | album sales
Carrie Underwood (Winner, 2005) | 28,580,000 (additional 1,043,000 featuring Randy Travis) | 14,578,000
Kelly Clarkson (Winner, 2002) |30,158,000 | 13,369,000
(Chris) Daughtry (2006) | 13,720,000 | 7,062,000
Clay Aiken (2003) | 674,000 | 5,019,000
Fantasia (Winner, 2004) | 1,856,000 | 3,176,000
Ruben Studdard (Winner, 2003) | 438,000 | 2,584,000
Scotty McCreery (Winner, 2011) | 2,738,000 | 2,012,000
Kellie Pickler (2006) | 4,189,000 | 1,514,000
David Cook (Winner, 2008) | 4,571,000 | 1,478,000
Jennifer Hudson (2004) | 2,605,000 | 1,347,000
Jordin Sparks (Winner, 2007) | 7,005,000 (additional 3,580,000 with Chris Brown) | 1,297,000
Phillip Phillips (Winner, 2012) | 7,472,000 | 1,255,000
Adam Lambert (2009) | 5,235,000 | 1,242,000
David Archuleta (2008) | 3,497,000 | 1,156,000
Josh Gracin (2003) | 1,432,000 | 804,000
Taylor Hicks (Winner, 2006) | 387,000 | 768,000
Bo Bice (2005) | 555,000 | 757,000
Katharine McPhee (2006) | 1,612,000 | 475,000
Lauren Alaina (2011) | 998,000 | 424,000
Kris Allen (Winner 2009) | 3,317,000 | 393,000
Top-selling singing-competition artists ranked by career sales in single-track downloads and albums (physical and digital). Source: Nielsen SoundScan