The CBO projects that the FY2014 budget deficit will be $514 billion, 3% of GDP, and will be just $478 billion or 2.6% of GDP in FY2015. The deficit then begins to rise as a percentage of GDP. A key reason: interest on the debt. While a manageable $233 billion or 1.3% of GDP today, debt service will reach $880 billion by 2024, a whopping 3.3% of projected 2024 GDP.