Harvard Kennedy School's Linda Bilmes explains our national debt and deficits, specifically what costs have added to both. Bilmes points to tax cuts, war spending in Iraq and Afghanistan, the Great Recession, stimulus spending and automatic spending as the main causes behind our national debt. She also offers solutions to lowering the debt, including reforming the tax system, reforming the formula that Americans qualify for entitlement programs and reducing federal spending. This year, 92nd Street Y's Campaign for the American Conversation offers you insight and analysis from the best minds at the Harvard Kennedy School. HKS is collaborating with us on American Conversation Essentials -- videos that explain the issues at play during this campaign year. The videos are the building blocks for your own conversations with friends, colleagues and even people you're not sure you agree with. Start with the information we offer here and then keep your mind open as you discuss the topics of the day.