The complete bullshit accounting practice of using ever-increasing spending and revenues as the starting point. This assumes that the private sector of an economy will grow at a steady pace regardless of government's interference by way of more regulations and removing the incentives to produce. Also allows political parties to cry over "cuts" which are in reality projecting spending increases below their current baseline.
John Boner announced $1T in cuts over ten years using baseline budgeting, but the actual numbers show steady increases in Federal Spending.