Simplify the following text for a Grade 11 native English-speaking person.
Original: The estimated population of the Denver-Aurora-Boulder Combined Statistical Area was 2,998,878 in 2007 ( 15th most populous CSA ) .
Simplified: In 2007 , the Denverâ `` Auroraâ `` Boulder Combined Statistical Area ( CSA ) had about 2,998,878 people .