Sugarland's 'The Incredible Machine' continues to produce precious metal, as the country superstars' fourth studio album has been certified platinum by the Recording Industry Association of America (RIAA), indicating sales of more than one million units. The certification marks the fourth consecutive platinum or multi-platinum album for the dynamic duo.

The latest certification boosts Sugarland's physical album sales to more than nine million copies, with an additional five million digital singles sold.

Sugarland members Jennifer Nettles and Kristian Bush credit the 'steampunk movement,' a branch of science fiction that imagines a world where humans evolve intellectually, but technology remains set in Victorian times, as the artistic muse behind the new album's progressive sound. The 11-song collection includes the smash hit 'Stuck Like Glue' and the current Top 20 single, 'Little Miss.'

"I describe it emotionally as bungee jumping and eating chocolate cake,' Jennifer says. "It's terrifying and gratifying, all at the same time."

Sugarland are set to begin their 2011 Incredible Machine tour this spring, beginning in Houston, Texas on March 3 and ending in their hometown of Atlanta, Ga. on October 22. Last year's leg of the tour was one of Pollstar's Top 50 North American Tours of 2010. Check out Sugarland's tour schedule here.