• by Wayne Friedman , April 15, 2010

Death, taxes, and perhaps, a decline in broadcast ratings are some of the surest things in this world.

For many notable shows, key 18-49 live-plus-same-day viewership has declined: NBC's "Heroes" sank 36.1% to a 2.3 rating; CBS' "CSI" slipped 31.3% to a 3.3; ABC's "Desperate Housewives" lost 20.8% to a 4.2; NBC's Law & Order: SVU" dropped 29.4% to a 2.4; "Law & Order" slid 28.6% to a 1.5; Fox's "Lie To Me" dropped 32.4% to a 2.5; CBS's "Medium" fell 29.2% to a 1.7; and CBS' "Numb3rs" lost 27.3% to a 1.6.

This analysis is from Brad Adgate, senior vice president and corporate media director, Horizon Media.

A wide variety of broadcast TV shows' overall total viewership totals also hit the skeds versus a year ago.

Some of the biggest declines -- 20% or more in total viewers -- have been "90210," "Cold Case," "CSI," "Fringe," "The Ghost Whisperer," "Gossip Girl," "Heroes," "Lie To Me," "Numb3rs," "Rules of Engagement," ABC's Saturday Night (College) Football, "Smallville" and "Supernatural."

Those with more modest declines between 10% and 20% include "24," "30 Rock," "American Idol" (results show), "ABC Saturday Movie" "America's Next Top Model," CBS' "Crimetime Saturday," "Criminal Minds," "CSI: Miami," "Dateline" (Sunday edition), "Desperate Housewives," "Extreme Makeover: Home Edition"; "Gary Unmarried," "Hell's Kitchen," "How I Met Your Mother", "Kitchen Nightmares," "Law & Order: SVU," "Law & Order (Saturday), "The Mentalist" and "The New Adventures of Old Christine."

The biggest-rated 18-49 show, "American Idol" -- its main Tuesday performance show edition -- is down 5.3% for the season so far: a 8.9 rating against the 9.4 rating of a year ago. But its results show, typically running Wednesday, get worse marks, down 11.7% to a 8.3 rating, so far.

Among the most improved shows, CBS's "Big Bang Theory" had the biggest rise year-to-year: a 34.3% hike to an average 4.7 rating. NBC's "Sunday Night Football" also showed strong gains: 16.1% higher to a 7.2 average rating.

CBS also did better with "NCIS," which rose 5.7% more to a 3.7 rating. The net's "Amazing Race" grew 3.2% to a 3.2 rating. CBS' fall edition of "Survivor: Gabon" was up 10.5% to a 4.2 rating from the 3.8 number of "Survivor: Samoa," its previous fall outing.

Fox's Sunday night lineup continued to be strong: "Family Guy" gained 2.9% to a 3.6 rating; "The Simpsons" lifted 6.5% to a 3.3 number; and "American Dad" showed no change at a 2.7.

NBC's "Biggest Loser" (fall edition) climbed 12.1% to a 3.7 number. The network's "Football Night in America" improved 16.7% to a 3.5 rating.

ABC's "Lost" had a 2.3% hike to a 4.5 average rating. "The Bachelor" showed no change with a 4.0 rating, also a positive.