The U.S. national debt is once again raising alarm bells. Federal borrowing from outside investors expanded rapidly over the past decade, totaling more than $15 trillion in 2018, and it is projected to grow even faster over the next ten years under current law. Major budget legislation signed by President Donald J. Trump, along with continued growth in entitlements and higher interest rates, will see the debt nearly double by 2028 [PDF], coming close to the size of the entire U.S. economy.

If the debt continues to grow at an unsustainable level, it could expose the country to a number of dangers, economists say. In the extreme, the risk rises that Washington’s lenders, many of whom are foreign, could suddenly lose confidence, demand higher interest rates, and potentially trigger a fiscal crisis. Short of that, the rising debt could gradually squeeze discretionary spending and deny the country tools it needs for security and economic stability. Bringing the debt into check, experts say, will likely require politically difficult decisions to either curb entitlement spending, significantly raise taxes, or both.