Social Security to Rise 2.7 Pct. in 2005 WASHINGTON - More than 47 million Americans receiving Social Security will get a 2.7 percent increase - an extra \$25, on average - in their monthly checks next year, but much of the increase will be eaten up by higher Medicare premiums.    The Social Security Administration announced the cost-of-living adjustment Tuesday, and the increase will start showing up in checks in January...