1974-2012: ONE US TV show led by black actress

Useful stat, and insight into the barriers that ethnicity still poses for black actresses: there were zero US TV dramas fronted by a black actress after 1974, until now (Oct 2012). Just a 38-year gap!!!
That would be a helpful stat to quote if ethnicity came up in your exam (wider context).
Article below URL.

American television's real Scandal

Why have audiences had to wait 38 years for a black female lead character?

• Sarah Hughes
• The Guardian, Monday 22 October 2012 21.30 BST

Kerry Washington, star of Scandal. Photograph: Craig Sjodin/ABC

When Scandal, the new drama about political corruption in the US capital starring Kerry Washington was first previewed in America, the show's creator Shonda Rhimes remarked, somewhat caustically: "I think we were at a place where a non-white actor can be the lead in a television series a long time ago – I just think that people have failed to cast the actors they should have been casting."

Surprisingly, Washington is the first black female lead on network television in 38 years. Not since 1974 when Tessa Graves starred as a policewoman in the blaxploitation show Get Christie Love! has a primetime US network show featured a black woman as the main character.
Since then the roles for black actresses have typically been limited to supportive friend or snappy sidekick. Most recently, former Doctor Who star Freema Agyeman landed a supporting role in the upcoming Sex and the City prequel, The Carrie Diaries, fellow Brit Gugu Mbatha-Raw played one half of a husband/wife spy team in the swiftly cancelled Undercovers and former reality star Nene Leakes had turns in Glee and sitcom The New Normal.
Even Miranda Bailey, arguably the strongest character on the show that made Shonda Rhimes's name – Grey's Anatomy – is frequently relegated to the sidelines in favour of another smooch between Meredith and McDreamy.