In a report issued in 2010, the authors found only 6 percent of U.S. students performing at the advanced level in mathematics, a percentage lower than those attained by 30 other countries. And the problem is not limited to top-performing students. In 2011, they showed that just 32 percent of 8th graders in the United States were proficient in mathematics, placing the U.S. 32nd when ranked among the participating international jurisdictions. Admittedly, American governments at every level have taken actions that would seem to be highly promising. Federal, state, and local governments spent 35 percent more per pupil--in real-dollar terms--in 2009 than they had in 1990. States began holding schools accountable for student performance in the 1990s, and the federal government developed its own nationwide school-accountability program in 2002. And, in fact, U.S. students in elementary school do seem to be performing considerably better than they were a couple of decades ago. Most notably, the performance of 4th-grade students on math tests rose steeply between the mid-1990s and 2011. After a half century of concern and efforts, the United States may finally be taking the steps needed to catch up. To find out whether the United States is narrowing the international education gap, the authors provide in this report estimates of learning gains over the period between 1995 and 2009 for 49 countries from most of the developed and some of the newly developing parts of the world. They also examine changes in student performance in 41 states within the United States, allowing them to compare these states with each other as well as with the 48 other countries. (Contains 4 figures.)