Question: 2014 Tokyo Marathon was the first of the series of events that were held, beginning in which year?

Context paragraphs:
Yuki Kawauchi: Yuki Kawauchi (川内優輝 , Kawauchi Yūki , born 5 March 1987) is a Japanese marathon runner.  He came to prominence after running the 2011 Tokyo Marathon in 2:08:37, finishing as the first Japanese and third overall.  He is known as the "citizen runner" given that he works full-time for the government of Saitama Prefecture and trains in his time off with his own expenses without any sponsorship.

Carver Wolverhampton City Marathon: The Carver Wolverhampton Marathon is an annual marathon that is part of a series of events which constitute the Carver Marathon City Marathon Events.  The other events occurring at the same time as the marathon include the Carver Wolverhampton Half Marathon, Banks's Run, Children's Run and a cycling event.  The marathon is held in Wolverhampton, England on September every year.  The main purpose of these events is to raise money for charity.

2014 Tokyo Marathon: The 2014 Tokyo Marathon (Japanese: 東京マラソン 2014 ) was the eighth edition of the annual marathon race in Tokyo, Japan and was held on Sunday, 23 February.  An IAAF Gold Label Road Race, it was the first World Marathon Majors event to be held that year and represented the second occasion that the Tokyo race was part of the elite-level marathon series.

2016 Tokyo Marathon: The 2016 Tokyo Marathon (Japanese: 東京マラソン 2016 ) was the tenth edition of the annual marathon race in Tokyo, Japan and was held on Sunday, 28 February.  An IAAF Gold Label Road Race, it was the first World Marathon Majors event to be held that year.

Tirfi Tsegaye: Tirfi Tsegaye Beyene (born 25 November 1984) is an Ethiopian long-distance runner who competes in marathon races.  She has won the Berlin Marathon, the Paris Marathon (in a course record), the Tokyo Marathon (also in course-record time), and the Dubai Marathon.  Her personal best of 2:20:18 hours came as winner of the 2014 Berlin Marathon.

World Marathon Majors: The Abbott World Marathon Majors, originally known as the World Marathon Majors, is a championship-style competition for marathon runners that started in 2006.  It comprises six annual races for the cities of Tokyo (starting in 2013), Boston, London, Berlin, Chicago and New York City (except 2012), a biennial race, the IAAF World Championships Marathon, and a quadrennial race, the Olympic Games Marathon.

2013 Tokyo Marathon: The 2013 Tokyo Marathon (Japanese: 東京マラソン 2013 ) was the seventh edition of the annual marathon race in Tokyo, Japan and was held on Sunday, 24 February.  An IAAF Gold Label Road Race, it was the first World Marathon Majors event to be held that year and represented the first occasion that the Tokyo race was part of the elite-level marathon series.

2015 Tokyo Marathon: The 2015 Tokyo Marathon (Japanese: 東京マラソン 2015 ) was the ninth edition of the annual marathon race in Tokyo, Japan and was held on Sunday, 22 February.  An IAAF Gold Label Road Race, it was the first World Marathon Majors event to be held that year and represented the third occasion that the Tokyo race was part of the elite-level marathon series.

Toronto Marathon: The Toronto Marathon, held annually in May, is a race from Mel Lastman Square, in the north end of Toronto, to Ontario Place.  The race was initially called the Canadian International Marathon, and was first held in 1995 under its current organizer.  The origins of the event trace back to 1977.  In 2003, its name was changed to the Toronto Marathon.  In 2008, it was again renamed for a new primary sponsor, GoodLife Fitness.  It was held previously on the third Sunday in October, the first Sunday after Canadian Thanksgiving, for 16 consecutive years.  Because of concerns that the Toronto Waterfront Marathon was being held three weeks prior lead to too many road closures, the Toronto Marathon is now run in May, beginning in 2011.  The event was temporarily held mid-May in 2011, due to other events in the City of Toronto that year.  The event is now held on the first Sunday in May, beginning in 2012.

Portland Marathon: The Portland Marathon is an annual marathon sporting event held in the city of Portland, Oregon.  The 2015 Portland Marathon was held Sunday, October 4, 2015.  The event begins at 7:00 a.m.  It was first held in 1972 and has been held every year since.  The marathon is generally held the first Sunday in October, with as many as 10,000 runners competing.  It features both full marathon and half marathon events, a Non-competitive Family Walk, and a Kid's Fun Run & Obstacle Course.  As of 2016, the marathon drew around 7,000 participants for the marathon and 3,000 for the half-marathon.

Supporting paragraphs: 2014 Tokyo Marathon World Marathon Majors
Answer: 2006