Question: In what year was the National Football League policy spearheaded by Dan Rooney established?

Context articles: Kevin Colbert
Joe Rooney (American football)
National Football League Coach of the Year Award
List of NFL champions (1920–69)
Dan Rooney
Los Angeles Chargers retired numbers
Art Rooney Award
2017 Pittsburgh Steelers season
Ralph Wilson
Rooney Rule

Kevin Colbert (born January 1957) is the general manager of the National Football League's Pittsburgh Steelers since the start of 2000.
 He is widely credited with putting together the Super Bowl XL and the Super Bowl XLIII teams in Pittsburgh along with owner Dan Rooney, president Art Rooney II, and coaches Bill Cowher and Mike Tomlin.
Joseph Patrick Rooney (August 28, 1898 – March 4, 1979) was a professional football player from Ottawa, Ontario.
 After attending high school in Virginia, Minnesota, Rooney made his professional debut in the early years of National Football League in 1923 with the Duluth Kelleys.
 He played for the Kelleys, Duluth Eskimos, Chicago Cardinals, Pottsville Maroons and Rock Island Independents during his 7-year career.
The National Football League Coach of the Year Award is presented annually by various news and sports organizations to the National Football League (NFL) head coach who has done the most outstanding job of working with the talent he has at his disposal.
 Currently, the most widely recognized award is presented by the Associated Press (AP), although in the past several awards received press recognition.
 First presented in 1957, the AP award did not include American Football League (AFL) teams. "
The Sporting News" has given a pro football coach of the year award since 1947 and in 1949 gave its award to a non-NFL coach, Paul Brown of the All-America Football Conference's Cleveland Browns.
 Other NFL Coach of the Year awards are presented by "Pro Football Weekly"/Pro Football Writers of America and the Maxwell Football Club.
 The United Press International (UPI) NFL Coach of the Year award was first presented in 1955.
 From 1960 to 1969, before the AFL–NFL merger, an award was also given to the most outstanding coach from the AFL.
 When the leagues merged in 1970, separate awards were given to the best coaches from the American Football Conference (AFC) and National Football Conference (NFC).
 The UPI discontinued the awards after 1996.
The National Football League champions, prior to the merger between the National Football League (NFL) and American Football League (AFL) in 1970, were determined by two different systems.
 The National Football League was established on September 17, 1920, as the American Professional Football Association (APFA).
 The APFA changed its name in 1922 to the National Football League, which it has retained ever since.
 From 1921 to 1931, the APFA/NFL determined its champion by overall win–loss record, with no playoff games; ties were not counted in the winning percentage total.
 The APFA did not keep records of the 1920 season; they declared the Akron Pros, who finished the season with an 8–0–3 (8 wins, 0 losses, 3 ties) record, as the league's first champions, by a vote of the owners.
 The Canton Bulldogs won two straight championships from 1922 to 1923, and the Green Bay Packers won three in a row from 1929 to 1931.
Daniel Milton Rooney (July 20, 1932 – April 13, 2017) was chairman of the Pittsburgh Steelers, an American football team in the National Football League (NFL), and son of the Steelers' founder, Art Rooney.
 Dan Rooney was elected to the Pro Football Hall of Fame in 2000 for his contributions to the game.
 He was credited with spearheading a requirement that NFL teams with head coach and general manager vacancies interview at least one minority candidate, which has become known as the "Rooney Rule".
The Los Angeles Chargers are a professional American football team in the National Football League (NFL) based in the Greater Los Angeles Area.
 The club began play in 1960 as a charter member of the American Football League (AFL), and spent its first season in Los Angeles before moving to San Diego in 1961.
 They returned to Los Angeles in 2017.
 NFL teams assign each of their players a jersey number ranging from 1 through 99.
 The Chargers no longer issue four retired numbers.
 As of 2010, the team's policy was to have the Chargers Hall of Fame committee evaluate candidates for a player's number to retire after the player has retired from the league after five years.
 The committee consisted of Chargers Executive Vice President A. G. Spanos, Chargers public relations director Bill Johnston, San Diego Hall of Champions founder Bob Breitbard, and the presidents of the San Diego Sports Commission and the Chargers Backers Fan Club.
 There are few recognized guidelines in sports regarding retiring numbers, and the NFL has no specific league policy.
 "You have to have enough numbers for players to wear," said NFL spokesman Greg Aiello.
 The Chargers have rarely retired numbers.
 The "San Diego Union-Tribune" wrote, "The [Chargers] tend to honor their heritage haphazardly."
The Art Rooney Award is given annually by the National Football League recognizing outstanding sportsmanship on the playing field.
 Established in 2015, the award is named in honor of Art Rooney, Sr., the founding owner of the Pittsburgh Steelers and a member of the National Football League Hall of Fame.
The 2017 Pittsburgh Steelers season is the franchise's 85th season as a professional sports franchise and as a member of the National Football League.
 It marks the 18th season under leadership of general manager Kevin Colbert and the eleventh under head coach Mike Tomlin.
 It is also the Steelers' first season without the ownership of Dan Rooney, as he died on April 13, 2017.
Ralph Cookerly Wilson Jr. (October 17, 1918 – March 25, 2014) was as an American businessman and sports executive.
 He was best known as the founder and owner of the Buffalo Bills, a team in the National Football League (NFL).
 He was one of the founding owners of the American Football League (AFL), the league with which the NFL merged in 1970, and was the last of the original AFL owners to own his team.
 At the time of his death he was the oldest owner in the NFL, at age 95, and the third-longest tenured owner in NFL history (over 54 years, behind the 63 years George Halas owned the Chicago Bears and almost equal to the 55 years Art Rooney owned the Pittsburgh Steelers, although Rooney's ownership and team operations were interrupted in the 1940s due to some complicated dealings).
 He was inducted into the Pro Football Hall of Fame in 2009.
The Rooney Rule is a National Football League policy that requires league teams to interview minority candidates for head coaching and senior football operation jobs.
 It is sometimes cited as an example of affirmative action, though there is no quota or preference given to minorities in the hiring of candidates.
 It was established in 2003, and variations of the rule are now in place in other industries.