The 'AA+' rating on Denver City and County, Colo.'s art museum bonds reflects: A strong and diverse economy, Above-average wealth and income levels, Moderately low debt, and Historically high fund balances and conservative budgeting practices. These factors are offset slightly by state constitutional limitations on revenues. A portion of the debt of the Denver Water Board is also backed by the general obligation of the city and is assigned the same rating as the city's GO bonds. These double-barreled bonds are considered self-supporting due to strong coverage of water system debt service by net water system revenues. Denver serves as a service, trade, and transportation center for the greater Rocky Mountain region. Although the city now estimates sales taxes declined