(FORTUNE Magazine) – They're the shadow government--the millions of private-sector contractors doing everything from Homeland Security--related IT projects here to interrogations in Iraq. Estimates vary, but Paul Light of the Brookings Institution puts the number of such workers at 5.6 million--roughly double the size of the federal workforce. Recently released figures show that federal funds committed to primary contractors jumped 50% from fiscal 2000, to $311 billion in fiscal 2004. And if contractors were a department, they'd rank second only to the Defense Department in terms of their annual budget. Here's a look at how fast the shadow government has grown. -- Peronet Despeignes