The American job market is on an historic roll. The even better news is that it's still got a lot of room for improvement. The February Jobs report, released Friday morning, was another good one. The U.S. added 295,000 jobs last month (economists predicted 240,00 new jobs). The unemployment rate dropped from 5.7 percent to 5.5 percent, the lowest it has been since May 2008. And yet there is a significant amount of what economists call "slack" -- people who can be put to better work in the economy without inflation becoming an issue.