Romney’s vow to cap federal spending at 20% of GDP by 2016, while maintaining defense spending at 4% of GDP and leaving both Social Security and Medicare unchanged for those 55 or older, implies exempting more than 50% of government spending from cuts for the next decade. So, to hit the 20% cap, spending on everything else would have to be slashed by an average of roughly 40% by 2016 and 57% by 2022.