About 20.6 million people watched President Obama's second inauguration on 18 broadcast and cable networks on Monday, down 46 percent from 37.8 million who tuned in for his first inauguration in 2009, Nielsen Media Research said on Wednesday. The drop-off was in line with similar second-term inaugurations. The number of viewers for George W. Bush's second-term swearing-in dropped to 15.5 million in 2005 from 29 million in 2001. Bill Clinton's dropped to 21.6 million in 1997 from 29.7 million in 1993, and Ronald Reagan's dropped to 18.9 million in 1985 from 41.8 million in 1981. Only Richard Nixon's inauguration has seen an uptick in viewers, rising 22 percent to 33 million in 1973 from 27 million in 1969.