Policy makers around the world are hard at work crafting stimulus packages filled with subsidies and protections they hope will breathe new life into their domestic economies, and preparing to rewrite the rules and regulations that govern global markets.

Why is this dangerous? At the G-20 summit a few weeks ago, world leaders pledged to address the crisis by coordinating their economic policy responses. That’s not going to happen, because politicians design stimulus packages with political motives — to satisfy the needs of their constituents — not to address imbalances in the global economy. This is as true in Washington as in Beijing. That’s why politics will drive the global economy more directly (and less efficiently) in 2009 than at any point in decades. Its politics that is creating the biggest risk for markets this year.