Five years after we entered a historic national recession, the U.S. economy is still only sputtering along.Some say the recession was just too deep to expect anything but a weak and prolonged recovery. Some say the stimulus was too small or poorly targeted. Or the plan to stabilize housing prices was too big or too small. Or government is taxing people too much or too little.All these issues made for interesting debates during the presidential campaign. But none explains why the national economy is still so weak. Thankfully, the urgency of avoiding the "fiscal cliff" is leading Congress and the White House toward a political agreement that would finally begin addressing the economy's chief underlying problem: the lack of confidence businesses and individuals have in Washington's ability to ensure stable market conditions.Business leaders -- large and small -- understand that Washington cannot continue running up massive deficits without producing collateral consequences, either higher interest rates, higher inflation or higher taxes. And when these outcomes are unknown, businesses play it safe -- by not investing.Unlike in the run-up to the 2008 crash, when businesses took too much risk, today they are not willing to take risks we need them to take. Businesses are sitting on record amounts of capital. By agreeing on a serious, credible plan to reduce the deficit, Washington will create the confidence about market stability that is necessary for that capital to be unleashed, creating new jobs and greater economic activity.Both parties in Washington and both ends of Pennsylvania Avenue view the fiscal cliff in political, rather than economic, terms. The White House is dead set on raising taxes, and Republicans are dead set on cutting spending -- both for their own ideological reasons. As it happens, doing both things is also one of the best possible ways to spur job growth. Call it accidental economics.The outlines of a solution that would give businesses the confidence to invest have been apparent for some time. Two years ago, the Simpson-Bowles commission outlined a solution that included tax increases and spending cuts. President Barack Obama did not endorse it, and Congress did not seriously consider it.A year ago, the bipartisan "supercommittee" on deficit reduction could not come to agreement on even a scaled-down version of Simpson-Bowles, despite strong support from business leaders. And then election-year politics prevented anything substantive from happening for the next 12 months. We do not need another commission or task force. We have waited too long already; it is time for action. There have been signs that Congress and the White House are beginning to move toward an agreement that would include modest tax increases and spending cuts, as well as a commitment to enact broader-based tax and entitlement reforms in 2013. While the tax revenue and entitlement cuts being discussed are both less than what I and many others believe are necessary to maximize long-term growth, the specifics of the deal are to some extent less important than the act of getting one.If the new year arrives and Washington goes over the fiscal cliff, the economic consequences could be quite severe, but not for the reasons most often discussed. If businesses see that Washington is still unable to deal with the most basic fiscal management issues, even when it is under enormous political pressure and facing a hard deadline, their investment plans for 2013 may be still further delayed, destroying countless jobs and further stalling a full recovery.The steps we need Congress to take to get the economy moving again do not require money; they require leadership. And that will require both parties and both ends of Pennsylvania Avenue to show flexibility on the two issues that have stood in the way of a deal for years: taxes and entitlement reform. If both parties believe they can reach a deal that allows them to claim political victory, the real winner will be the American economy and the 12 million people who are looking for work.Michael Bloomberg, an independent, is mayor of New York.