Supreme Court justices cooperate strategically to strengthen coalitions

The past year has seen major decisions by the Supreme Court on gay marriage and Obamacare. But what influences the coalitions of opinion in Supreme Court decisions? In new research that examines nearly 30,000 choices by Supreme Court justices over 40 years, Andrew J. O’Geen and Christopher M. Parker find that when a decision’s initial majority is small, justices are much less likely to write separate opinions in order to stabilize the shaky majority.