• by Wayne Friedman , March 21, 2014

Though CBS network viewership might be down for the NCAA Tournament, overall TV coverage of all national TV networks has posted viewership gains versus as year ago -- and highest overall since the tournament has gone to a four network window in 1991.

Four TV networks -- CBS, TBS, TNT and truTV -- combined household ratings on Thursday, March 20, the first day of the tournament, averaged a Nielsen 6.0 rating/14 share -- up 3% from the 5.8/14 results from the first day of the March Madness tournament a year ago.

CBS says the overall tournament average rating, including the NCAA First Four games, is at 5.6/12, up 8% from a 5.2/12 last year, and is also the highest rating for the tournament at this point in the event since 1991.

CBS says viewership was the highest its been in all dayparts --- daytime, late afternoon, early and late evening. The 12:00 noon to 4:45 p.m ET averaged a 4.6/15 up 12% compared with a 4.1/14 last year. The 2:45 p.m. to 7:15 p.m window was at  5.4/14 to garner the second-highest rating for the time slot since 1991.

Both prime-time periods grew as well: The 6:45 p.m. to 10:30 p.m. window at a 7.7/15 to register up 4% over a 7.4/14 in 2013; with the second prime-time window, 9:30 p.m. to 1:45 a.m. at a 6.2/12.

For its parts on the CBS network, the first game between 8 and 9:17 p.m, -- Wofford/Michigan -- earned a Nielsen 1.0/4 and 3.8 million overall viewers. The second game Arizona State-Texas, 9:18 p.m. -- 12:04 a.m. -- earned a 1.3/4 and 3.7 million viewers.