Question: Strictly Come Dancing returned for its twelfth series beginning from 7 September 2014 with a launch show, with the live shows starting on 26 and 27 September, Bruce Forsyth decided to leave the show after the eleventh series; however, Forsyth will continue to host the Christmas specials, titled Christmas Specials of "Strictly Come Dancing", and have been transmitted by BBC Television, each year since which year?

Context paragraphs:
Strictly Come Dancing (series 11): Strictly Come Dancing returned for its eleventh series beginning with a launch show on 7 September 2013, with the live shows starting on 27 and 28 September 2013.  Bruce Forsyth and Tess Daly continued to co-present the main show on BBC One, with Claudia Winkleman returning to present the results show alongside Daly.  Zoë Ball returned as presenter of "" on BBC Two.  Len Goodman, Bruno Tonioli, Craig Revel Horwood and Darcey Bussell also returned as judges.

Strictly Come Dancing (series 9): Strictly Come Dancing returned for its ninth series on 10 September 2011 with a launch show, with the live shows starting on 30 September and 1 October 2011.  The show was broadcast from Wembley Arena on 19 November with all proceeds going to the BBC charity, Children in Need.  The final took place at the Blackpool Tower Ballroom and was the first episode in 3D, and was shown on BBC HD and 18 cinemas around the country.  As in series 8 there are 14 couples with one new male professional, Pasha Kovalev, replacing Jared Murillo.

Strictly Come Dancing Christmas Specials: The Christmas Specials of "Strictly Come Dancing" have been transmitted by BBC Television each year since 2004.  Early editions contained a selection of contestants from the most recent and occasionally previous seasons of the show, however from the 2010 special to the 2013 special, the competition has been contested by celebrities who are unable to compete in the main series due to time constrictions.  With their professional dance partners the celebrities perform their chosen Ballroom or Latin dance which is then marked by the judges.  The winning couple is chosen by a studio audience vote.

Strictly Come Dancing (series 4): Strictly Come Dancing returned for its fourth series on 7 October 2006 and ended on 23 December.  Bruce Forsyth and Tess Daly returned to co-present the main show on BBC One, whilst Claudia Winkleman returned to present spin-off show "" on BBC Two for the third series in a row.  Len Goodman, Bruno Tonioli, Craig Revel Horwood and Arlene Phillips returned as judges.  The winner was Mark Ramprakash and his dancing partner Karen Hardy.

Strictly Come Dancing (series 12): Strictly Come Dancing returned for its twelfth series beginning from 7 September 2014 with a launch show, with the live shows starting on 26 and 27 September.  Tess Daly returned to present the main show on BBC One alongside Claudia Winkleman, who has been promoted to co-presenter in addition to the results show after Bruce Forsyth decided to leave the show after the eleventh series; however, Forsyth will continue to host the Christmas and Children in Need specials.  Zoë Ball returned as presenter of spin-off show "" on BBC Two.  Judges Len Goodman, Bruno Tonioli, Craig Revel Horwood and Darcey Bussell also returned.

Strictly Come Dancing (series 15): Strictly Come Dancing returned for its fifteenth series with a launch show on 9 September on BBC One, with the live shows starting on 23 September 2017.  Tess Daly and Claudia Winkleman returned as hosts, while Zoë Ball returned to host "" on BBC Two.  Bruno Tonioli, Craig Revel Horwood, and Darcey Bussell returned as judges.  On 9 May 2017, it was announced that Len Goodman would be replaced by Shirley Ballas due to Goodman's retirement from the show.  This is the first series to have 2 female and 2 male judges on the panel.

Strictly Come Dancing (series 14): Strictly Come Dancing returned for its fourteenth series with a launch show on 3 September on BBC One, with the live shows starting on 23 September 2016.  Tess Daly and Claudia Winkleman returned as hosts, while Zoë Ball returned to host "" on BBC Two.  Len Goodman, Bruno Tonioli, Craig Revel Horwood and Darcey Bussell returned as judges.  This was Goodman's final series as a judge.

Strictly Come Dancing (series 2): Strictly Come Dancing returned for its second series on 23 October 2004 on BBC One.  Bruce Forsyth and Tess Daly returned to present the main show on BBC One, while Claudia Winkleman presented a new spin-off show called "" on BBC Two.  Series 1 winner Natasha Kaplinsky filled in for Daly during the first five weeks due to maternity leave.  Len Goodman, Bruno Tonioli, Craig Revel Horwood and Arlene Phillips returned to the judging panel.

Strictly Come Dancing (series 10): Strictly Come Dancing returned for its tenth series and began with the launch show on 15 September 2012.  The live shows commenced on 5 October.  Fourteen celebrities took part - the same number as the previous year.  Bruce Forsyth and Tess Daly returned to present the main show on BBC One and Claudia Winkleman returned to present the results show with Daly.  Zoë Ball returned to present spin-off show "".  Judges Len Goodman, Bruno Tonioli and Craig Revel Horwood all returned and were joined on the judging panel by series 7 guest judge Darcey Bussell, who replaced Alesha Dixon.

Strictly Come Dancing (series 13): Strictly Come Dancing returned for its thirteenth series on BBC One with a launch show on 5 September 2015, with the live shows starting on 25 September 2015.  Tess Daly and Claudia Winkleman returned to present the launch show and the live shows while Zoë Ball returned to present "" on BBC Two.  Len Goodman, Bruno Tonioli and Craig Revel Horwood returned as judges for their thirteenth series, along with Darcey Bussell who returned for her fourth series as a judge.

Supporting paragraphs: Strictly Come Dancing (series 12) Strictly Come Dancing Christmas Specials
Answer: 2004