CBO's budget outlook, little changed since its last update, shows the same story it has for a few years: the debt picture will stabilize through about the end of the decade, but then will grow by nearly 5 percentage points of GDP between 2020 and 2025 from 74 to 79 percent of GDP.
Simply stabilizing the debt at current levels would require $1.3 trillion of deficit reduction over a decade, while putting debt on a downward path as a share of GDP -- a minimum standard of sustainability -- would require $2.4 trillion of savings.
In previous iterations of CBO's baseline, we showed an illustrative savings path that would leave debt clearly declining as a percent of GDP. For example, in May 2013, we showed that it would take $2.2 trillion of savings over ten years compared to our realistic baseline to put debt on a downward path to 67 percent by 2023. We used this level because the downward path proved robust to having more frontloaded savings, worsening economic projections, and lawmakers enacting deficit-increasing policies.
However, two years have now passed and CBO's projections worsened in the meantime, so the target could be somewhat more lax but require higher savings. Getting debt to 70 percent of GDP by 2025 would take $2.4 trillion of savings compared to CBO's baseline. We estimate that a reasonably backloaded plan of this magnitude would put the trajectory of debt on a clear downward path, and leave deficits in a consistent decline to about 2 percent of GDP by 2025 (instead of deficits increasing as a percent of GDP after 2016 under current law). Of course, actual plans may vary and the extent to which they would ensure long-term sustainability depends greatly on the types of policies included.