Economists watch Congress the way that ancient Sumatrans watched the volcano at Krakatoa: They don’t really understand at all what’s going on inside the caldera but they smell the ash and know there’s some chance of a catastrophic explosion. In recent years, economists have been forced to heed the rumblings from Congress: The U.S. has had several close calls leading to tremors in financial markets, including a government shutdown lasting more than two weeks in 2013 and a near-default on the U.S. debt in 2011 that led to a downgrade of the U.S. triple-A debt rating.