It’s a pretty cool name for an otherwise drab concept. Yet, firewalls should matter to anyone who cares about government’s ability to promote economic growth, broadly shared prosperity, and social justice. Let’s start from the beginning, with the entire budget at $3.5 trillion (budget authority in 2011). Set aside mandatory programs—such as Social Security, Medicare, Medicaid, unemployment insurance, and other social safety net programs—and interest payments. All told, that’s about $2.1 trillion of the budget, or two-thirds of the total. The remaining third of the budget is discretionary spending, about 58 percent of which is defense and war spending. The rest (the green slice) is everything else: homeland security, veterans benefits, roads and bridges, education, energy , health, and environmental research, consumer protection, law and order, community development… it’s all in there. This portion of the budget, which comprises a paltry 14 percent of the total, is referred to with the exciting name “non-defense discretionary.”

Because discretionary spending is appropriated each year, Congress can only cut it for the current or upcoming budget year. Instead, it can cap discretionary spending, as it did last August when it passed the Budget Control Act (BCA). These caps act as procedural obstacles to appropriating more than a specified amount in future years (also known as “out-years”). BCA institutes caps on the out-years, but only a single discretionary cap (excluding war spending). This worried progressives because it could allow conservatives in Congress to increase spending on the Department of Defense and pay for the increase with even further reductions in non-defense. In other words, it would provide conservatives with a double-win: They get to spend more on the Department of Defense even as the rest of the government faces cuts, and they get to use those defense increases to their advantage, to force even larger cuts to the non-defense budget than would otherwise be required if the entire discretionary budget were cut proportionately. This is where firewalls come in. Earlier this month, the Office of Management and Budget and the Congressional Budget Office each released an update on what happens next now that the Super Committee has failed. Most people have been focused on the sequestration provisions, which don’t take effect until 2013 (and will be heavily impacted by the election outcome). But, quietly, something else happened: As per the BCA law, automatic firewalls between defense and non-defense are now the law of the land. We should always be worried that conservatives will play the defense budget against the non-defense budget, but the new caps, which put separate limits on defense and non-defense, will make that eminently more difficult. And without further ado, here are your new budget caps!

And a little historical context…

Obviously, this isn’t exactly shared sacrifice. Non-defense discretionary, at 3.2 percent of GDP, is already below the 35-year average of 3.9 percent. Yet these caps cut this portion of the budget by almost $100 billion more than the defense budget, bringing it down to 2.5 percent of GDP, the lowest level in more than 35 years (as far as the budget authority data extends).