The national television rating for the final hour of the Kentucky Derby broadcast on NBC-TV on Saturday afternoon was an 8.5 with a 19 share, down 13.3 percent compared with the 9.8 rating share for the race portion of the broadcast in both 2010 and 2009, according to figures released by the network.\r\nThe rating figure translated into an average audience of 14.5 million viewers from 6:06 p.m. Eastern until 6:56 p.m., according to calculations provided by Neilsen, the ratings measurement company. The viewership figure was down 12 percent from last year&rsquo;s figure of 16.5 million, which was the highest for a Kentucky Derby broadcast since 1989, according to NBC.\r\nFinal figures for the entire three-hour broadcast on NBC will be available on Thursday, according to Adam Freifeld, a spokesman for NBC.\r\nFreifeld said that the rating this year suffered from the lack of a sports lead-in to the broadcast, which began at 4 p.m. Eastern after five hours of live coverage on Versus, a cable network owned by NBC. In the two previous years, live NHL hockey playoff games had provided the lead-in to the Derby broadcast, but this year, the broadcast was preceded by local affiliate programming.\r\nFreifeld also said that good weather in major markets may have negatively impacted the rating. In Louisville, for example, the rating was a 34.4 this year, down from 45.4 last year, when thunderstorms limited the entertainment options for the city's residents. This year, the weather in Louisville was pleasant.\r\n&ldquo;While [the national rating] is down a little bit, it&rsquo;s still a strong number,&rdquo; Freifeld said. The Derby is typically the highest-rated sports broadcast of the weekend on which the event is held.\r\nNBC, which will broadcast all three races of the Triple Crown this year for the first time since 2005, has been heavily promoting coverage of the races.