Our final pie of Pie Week! We showed you total federal spending, mandatory spending, and discretionary spending. Today's flavor of pie? Where the money comes from to fund the federal budget.

Tomorrow we'll review all the great kinds of pie we brought your way this week.

In his last post, my research colleague Chris Hellman explained where we are in the annual federal budget process. He noted that President Obama released a budget in February; the House passed a very different budget in March; and the Senate has declined to do a budget. The seeds are planted for stalemate this election year, Chris wrote. If Congress cannot pass a budget for President Obama to sign by Oct. 1 – which is the start of fiscal year 2013 – then lawmakers will have to pass temporary spending legislation, called continuing resolutions, to fund the federal government.

Why can't ...