Michael Sparer

Today the Supreme Court upheld the constitutionality of various parts of "Obamacare" -- most notably the individual mandate. Live coverage and analysis from:

• Todd Zwillich, Takeaway Washington correspondent, live on the steps of the Supreme Court
• Columbia's Michael Sparer, chair of Health Policy and Managment
• Avik Roy, senior fellow at the Manhattan Institute, and author of The Apothecary blog on healthcare policy for Forbes

Plus, your calls and more.

More than half of all Americans who have health insurance belong to health maintenance organizations, more commonly called HMOs. On today's Please Explain, Professor Michael Sparer of Columbia University's Mailman School of Public Health will answer your questions about the history of HMOs, how they work, how plans differ from ...