Nielsen Media Research has once again adjusted its ratings system to reflect changes in the growth of the U.S. population. As of next week, ratings will be based on 112.8 million TV households versus the current 111.3 million, an increase of 1.3 percent. Each ratings point will therefore now represent 1.13 million viewers. In the key 18-49 adults category each rating point will represent 1.31 million viewers (virtually flat with the current number). However, reflecting the aging of the baby-boom generation, the 55-64 demographic group increased by 3.8 percent. Nielsen has also realigned its list of markets by size. In the top ten, two significant changes occurred: Dallas-Fort Worth moved up a notch to fifth place from sixth, changing places with San Francisco-Oakland. Atlanta moved to eighth place from ninth, switching with Washington D.C.