Question: How long did the original broadcaster of the series that has the episode Known Unknowns, reign in the 18-49 Nielsen demographics?

full_context: Document 1: Knight Fall: "Knight Fall" is the eighteenth episode of the sixth season of the American medical drama "House" and it is the 127th episode overall. It aired on April 19, 2010 and was directed by Juan J. Campanella.
Document 2: Perils of Paranoia: "Perils of Paranoia" is the eighth episode of the eighth season of the American television medical drama series "House" and the 163rd overall episode of the series. It aired on Fox on November 28, 2011.
Document 3: I Saw What I Saw: "I Saw What I Saw" is the sixth episode of the sixth season of the American television medical drama "Grey's Anatomy", and the show's 108th episode overall. It was written by Peter William Harper and directed by Allison Liddi-Brown. The episode was originally broadcast on the American Broadcasting Company (ABC) in the United States on October 22, 2009.
Document 4: House (TV series): House (also called House, M.D.) is an American television medical drama that originally ran on the Fox network for eight seasons, from November 16, 2004 to May 21, 2012. The series' main character is Dr. Gregory House (Hugh Laurie), an unconventional, misanthropic medical genius who, despite his dependence on pain medication, leads a team of diagnosticians at the fictional Princeton -- Plainsboro Teaching Hospital (PPTH) in New Jersey. The series' premise originated with Paul Attanasio, while David Shore, who is credited as creator, was primarily responsible for the conception of the title character. The series' executive producers included Shore, Attanasio, Attanasio's business partner Katie Jacobs, and film director Bryan Singer. It was filmed largely in a neighborhood and business district in Los Angeles County's Westside called Century City.
Document 5: American Idol: The declining trend however continued into season eight, as total viewers numbers fell by 5–10% for early episodes compared to season seven, and by 9% for the finale. In season nine, Idol's six-year extended streak of perfection in the ratings was broken, when NBC's coverage of the 2010 Winter Olympics on February 17 beat Idol in the same time slot with 30.1 million viewers over Idol's 18.4 million. Nevertheless, American Idol overall finished its ninth season as the most watched TV series for the sixth year running, breaking the previous record of five consecutive seasons achieved by CBS' All in the Family and NBC's The Cosby Show.
Document 6: American Idol: The loss of viewers continued into season 12, which saw the show hitting a number of series low in the 18-49 demo. The finale had 7.2 million fewer viewers than the previous season, and saw a drop of 44% in the 18-49 demo. The season viewers averaged at 13.3 million, a drop of 24% from the previous season. The thirteenth season suffered a huge decline in the 18–49 demographic, a drop of 28% from the twelfth season, and American Idol lost its Top 10 position in the Nielsen ratings by the end of the 2013–14 television season for the first time since its entry to the rankings in 2003 as a result, although the entire series to date had not yet been dropped from the Nielsen Top 30 rankings since its inception in 2002.
Document 7: Known Unknowns: "Known Unknowns" is the seventh episode of the sixth season of "House" and 117th overall. It aired on November 9, 2009. The team tries to diagnose a teenage girl while House is away at a medical conference with Wilson and Cuddy. At the conference House finds something out about Cuddy.
Document 8: American Idol: Season eleven, however, suffered a steep drop in ratings, a drop attributed by some to the arrival of new shows such as The Voice and The X-Factor. The ratings for the first two episodes of season eleven fell 16–21% in overall viewer numbers and 24–27% in the 18/49 demo, while the season finale fell 27% in total viewer number and 30% in the 18-49 demo. The average viewership for the season fell below 20 million viewers the first time since 2003, a drop of 23% in total viewers and 30% in the 18/49 demo. For the first time in eight years, American Idol lost the leading position in both the total viewers number and the 18/49 demo, coming in second to NBC Sunday Night Football, although the strengths of Idol in its second year in the Wednesday-Thursday primetime slots helped Fox achieve the longest period of 18-49 demographic victory in the Nielsen ratings, standing at 8 straight years from 2004 to 2012.
Document 9: Abby Lockhart: At the end of the thirteenth season, Abby and Luka plan to honeymoon in Hawaii. However, the night before they are due to depart, Luka receives a phone call from Croatia informing him that his father is ill, so the honeymoon is put on hold until Luka can return from his urgent trip abroad. After Luka's departure, Abby has a tough time with the stern new ER Chief Kevin Moretti, who plans to mold the department into a more efficient and professional work environment, but Moretti quickly tells Abby he is very impressed with her work. Despite this, she seems to dislike him more than many of the other residents. In season 14, Abby is struggling to deal with Luka's absence, raise Joe and work at the ER; in ``Gravity '', Joe is injured after falling off a jungle gym at the playground and Abby ends up falling back into drinking at the episode's end. She approaches Dr. Janet Coburn (the O.B. Chief) who appears to have been her AA sponsor in the past. Abby's drinking problem continues to escalate, and she realizes how bad it is in`` Blackout'' when she shows up drunk to a party in honor of Pratt and Morris passing their boards. Abby finds herself waking up at 3am in Moretti's apartment realizing, after sobering up at the airport when trying to find a flight to Croatia to see Luka, that she slept with him.
Document 10: American Idol: In season ten, the total viewer numbers for the first week of shows fell 12–13%, and by up to 23% in the 18–49 demo compared to season nine. Later episodes, however, retained viewers better, and the season ended on a high with a significant increase in viewership for the finale – up 12% for the adults 18–49 demo and a 21% increase in total viewers from the season nine finale. While the overall viewer number has increased this season, its viewer demographics have continued to age year on year – the median age this season was 47.2 compared to a median age of 32.1 in its first season. By the time of the 2010–11 television season, Fox was in its seventh consecutive season of victory overall in the 18–49 demographic ratings in the United States.
Document 11: Allison Cameron: Allison Cameron, M.D., is a fictional character on the Fox medical drama "House", portrayed by American actress Jennifer Morrison. An immunologist, Cameron was a member of Dr. Gregory House's team of handpicked specialists at Princeton-Plainsboro Teaching Hospital's Department of Diagnostic Medicine. She returned for the final episode of the series, "Everybody Dies".
Document 12: 97 Seconds: "97 Seconds" is the third episode of the fourth season of "House" and the seventy-third episode overall. It aired on October 9, 2007.
Document 13: American Idol: The loss of viewers continued into season seven. The premiere was down 11% among total viewers, and the results show in which Kristy Lee Cook was eliminated delivered its lowest-rated Wednesday show among the 18–34 demo since the first season in 2002. However, the ratings rebounded for the season seven finale with the excitement over the battle of the Davids, and improved over season six as the series' third most watched finale. The strong finish of season seven also helped Fox become the most watched TV network in the country for the first time since its inception, a first ever in American television history for a non-Big Three major broadcast network. Overall ratings for the season were down 10% from season six, which is in line with the fall in viewership across all networks due in part to the 2007–2008 Writers Guild of America strike.
Document 14: List of House episodes: "House", also known as "House, M.D.", is an American medical drama series which premiered on Fox on November 16, 2004. "House" was created by David Shore. The show follows Dr. Gregory House (Hugh Laurie), an irascible, maverick medical genius who heads a team of diagnosticians at the fictional Princeton-Plainsboro Teaching Hospital (PPTH) in New Jersey. In a typical episode, the team is presented with an unusual case; the storyline follows the diagnosis of the patient's illness, a process often complicated by the internal competition and personal foibles of the diagnostic team. The team leader, House, frequently clashes with his boss (Dr. Lisa Cuddy (Lisa Edelstein) in seasons 1 through 7, and Dr. Eric Foreman in season 8), and his only friend, Dr. James Wilson (Robert Sean Leonard).
Document 15: Gregory House: Gregory House, M.D., commonly referred to by his surname House, is the title character of the American medical drama series House. Created by David Shore and portrayed by English actor Hugh Laurie, he leads a team of diagnosticians as the Head of Diagnostic Medicine at the fictional Princeton - Plainsboro Teaching Hospital in Princeton, New Jersey (based on the real - life Yale -- New Haven Hospital in New Haven, Connecticut).
ground_truth: eight years
sub_queries: Of what series is Known Unknowns a part of? Answer: House
House >> original broadcaster Answer: Fox
How long did Fox reign in the 18-49 demographics in the Nielsen ratings? Answer: eight years