The answer is yes. And no.

Yahoo! Music’s Paul Grein looked at the chart success of “Idol” alums and did the math with some interesting results.

When Kelly Clarkson sold 255,000 copies of All I Ever Wanted in the week that ended Sunday night, she lengthened her lead as the “American Idol” alumnus who has sold the most albums. This brings her career total to 9,836,000 albums. Still, it’s probably just a matter of time until Carrie Underwood overtakes her. Underwood, the Season 4 champ, has already sold 9,408,000 albums. These two women are the only “Idol” alums who rank among the top 200 album sellers of the Nielsen/SoundScan era (which began in 1991). Clarkson is #187 on the list. Underwood ranks #198. In all, eight “Idol” contestants have sold 1 million or more albums so far in their careers. Fifteen have sold 500,000 or more.

The best-selling individual album by an “Idol” alum is Underwood’s Some Hearts, which has sold 6,720,000 copies since its release in November 2005. It edges out Clarkson’s Breakaway, which has sold 6,056,000 copies. (Oddly, neither album made #1 on The Billboard 200. Some Hearts peaked at #2. Breakaway reached #3). The rest of the top five in terms of total sales: Daughtry‘s Daughtry (4,401,000), Clay Aiken‘s Measure Of A Man (2,783,000) and Clarkson’s Thankful (2,719,000).

So it looks like longevity is the key to claiming the top spot for the moment. Clarkson has three years on Underwood. And despite some questionable career choices early on (“From Justin to Kelly” anyone?), she seems to have stabilized into a long-term artist.

But wait, not everyone buys albums these days. Lots of people just download the songs they like. So who wins that contest?

The song with the most paid downloads by an “Idol” alum is “No Air,” Jordin Sparks‘ melodramatic duet with Chris Brown, which has sold 2,874,000 digital copies. It edges out Underwood’s revenge saga “Before He Cheats” (2,673,000). The rest of the top five: Clarkson’s turbo-charged “Since U Been Gone” (2,063,000), Daughtry’s rock ballad “It’s Not Over” (1,978,000) and Sparks’ gently rhythmic “Tattoo” (1,927,000).

The most surprising result of Grein’s analysis is which season of “Idol” produced the most hit-makers.

Four of the 15 “Idol” contestants who have sold the most albums competed in Season 5. They are Taylor Hicks, that season’s winner; Elliot Yamin, who came in third; Chris Daughtry, who finished fourth; and Kellie Pickler, who placed sixth. Though Hicks won the competition, all three of these other finalists have outsold him. (Hicks isn’t the only “Idol” winner who has been humbled on the charts by a singer he beat on the show. Ruben Studdard, the Season 2 winner, has been outsold by runner-up Clay Aiken.)

So does that mean “Idol” peaked in 2006? Probably. Ratings went south in a big way last season and producers of the show have done a lot of tinkering with the formula this year (fewer audition shows, more half hour episodes, a fourth judge) – never a good sign.

Fans of “Idol” shouldn’t fret too much though, it’s a safe bet the show’s creators are hard at work right now creating the next cash cow competition extravaganza.

Read Paul Grein’s complete list of “Idol” alum album sellers here.