Here’s hoping that red ink is erasable. The US economy actually grew in the fourth quarter of 2012—but just barely—instead of contracting for the first time in three and a half years, according to the Commerce Department. The US expanded at a 0.1% annual rate in the last three months of 2012, better than the initially reported 0.1% drop but well below the third quarter’s 3.1% pace. Stronger residential construction and an improvement in net exports pushed growth into positive territory. It of...