Question: What rank does the city where Everfree's author was born hold as far as being an economically powerful city in the world?

full_context: Document 1: William Sleator: William Warner Sleator III (February 13, 1945 – August 3, 2011), known as William Sleator, was an American science fiction author who wrote primarily young adult novels but also wrote for younger readers. His books typically deal with adolescents coming across a peculiar phenomenon related to an element of theoretical science, then trying to deal with the situation. The theme of family relationships, especially between siblings, is frequently intertwined with the science fiction plotline.
Document 2: Everfree: Everfree is a novel by Nick Sagan. It is the sequel to "Edenborn" and the final installment of this trilogy.
Document 3: Idlewild (novel): Idlewild is a science fiction novel by Nick Sagan, published in 2003. It is the first of a trilogy, with sequels "Edenborn" and "Everfree". The story is split between two settings: the middle of the 21st century (told through interludes and distinguished from the main story by italics) and a generation later. It is a picture of the last ten people on earth, a near-complete pantheon of gods and goddesses.
Document 4: Scott Young (writer): Scott Alexander Young (April 14, 1918 – June 12, 2005) was a Canadian journalist, sportswriter, novelist and the father of musicians Neil Young and Astrid Young. Over his career, Young wrote 45 books, including novels and non-fiction for adult and youth audiences.
Document 5: Ben Dolnick: Ben Dolnick was born and raised in Chevy Chase, Maryland. He is the son of Lynn Iphigene (née Golden) and Edward Dolnick; and a nephew of Arthur Golden, author of "Memoirs of a Geisha". Through his mother's side he is a member of the Ochs-Sulzberger family, publishers of "The New York Times". He attended Georgetown Day School and went on to receive his undergraduate degree from Columbia University, and has worked as a "zookeeper at the Central Park Zoo. He currently lives in Brooklyn, New York.
Document 6: New Delhi: The 2011 World Wealth Report ranks economic activity in New Delhi at 39, but overall the capital is ranked at 37, above cities like Jakarta and Johannesburg. New Delhi with Beijing shares the top position as the most targeted emerging markets retail destination among Asia-Pacific markets.
Document 7: The Infinite Sea: The Infinite Sea is a young adult science fiction novel written by American author Rick Yancey. It was published on September 16, 2014 by G.P. Putnam's Sons. The novel is the second in The 5th Wave trilogy, preceded by The 5th Wave and followed by The Last Star. After fleeing from a camp established by aliens, 16 - year - old Cassie Sullivan, her brother and a squad of child soldiers attempt to prevent the extermination of the human race.
Document 8: The 5th Wave (series): The 5th Wave is a trilogy of young adult post-apocalyptic sci - fi novels written by American author Rick Yancey. The series started in May 2013 with the first book, The 5th Wave. A sequel titled The Infinite Sea was published in 2014. The trilogy concluded in 2016 with the final book, The Last Star.
Document 9: Nick Sagan: Nick Sagan (born September 16, 1970 in Boston, Massachusetts) is an American novelist and screenwriter. He is the author of the science fiction novels "Idlewild", "Edenborn", and "Everfree", and his screen credits include episodes of "" and "". He is the son of astronomer Carl Sagan and artist and writer Linda Salzman.
Document 10: Magnus Chase and the Gods of Asgard: The Ship of the Dead is the third and final book in the Magnus Chase and the Gods of Asgard series and was released on October 3, 2017.
Document 11: New York City: New York is a global hub of international business and commerce. In 2012, New York City topped the first Global Economic Power Index, published by The Atlantic (to be differentiated from a namesake list published by the Martin Prosperity Institute), with cities ranked according to criteria reflecting their presence on similar lists as published by other entities. The city is a major center for banking and finance, retailing, world trade, transportation, tourism, real estate, new media as well as traditional media, advertising, legal services, accountancy, insurance, theater, fashion, and the arts in the United States; while Silicon Alley, metonymous for New York's broad-spectrum high technology sphere, continues to expand. The Port of New York and New Jersey is also a major economic engine, handling record cargo volume in the first half of 2014.
Document 12: Paul Sagan: Paul Sagan (born 1959) is an American businessman and managing partner at General Catalyst Partners. A three-time Emmy award winner for broadcast journalism in New York, Sagan began his career at WCBS-TV as a news writer and news director. Joining Time Warner to design and launch NY1, in 1995 he was named president and editor of new media at Time Inc. Sagan joined Akamai Technologies in 1998, becoming CEO in 2005. In 2014, he became a venture capitalist at General Catalyst Partners. He became chairman of the Massachusetts Board of Elementary and Secondary Education in 2015.
Document 13: Boston: Tourism also composes a large part of Boston's economy, with 21.2 million domestic and international visitors spending $8.3 billion in 2011; excluding visitors from Canada and Mexico, over 1.4 million international tourists visited Boston in 2014, with those from China and the United Kingdom leading the list. Boston's status as a state capital as well as the regional home of federal agencies has rendered law and government to be another major component of the city's economy. The city is a major seaport along the United States' East Coast and the oldest continuously operated industrial and fishing port in the Western Hemisphere.
Document 14: Boston: A global city, Boston is placed among the top 30 most economically powerful cities in the world. Encompassing $363 billion, the Greater Boston metropolitan area has the sixth-largest economy in the country and 12th-largest in the world.
Document 15: Boston: Boston is an intellectual, technological, and political center but has lost some important regional institutions, including the acquisition of The Boston Globe by The New York Times, and the loss to mergers and acquisitions of local financial institutions such as FleetBoston Financial, which was acquired by Charlotte-based Bank of America in 2004. Boston-based department stores Jordan Marsh and Filene's have both been merged into the Cincinnati–based Macy's. Boston has experienced gentrification in the latter half of the 20th century, with housing prices increasing sharply since the 1990s. Living expenses have risen, and Boston has one of the highest costs of living in the United States, and was ranked the 129th most expensive major city in the world in a 2011 survey of 214 cities. Despite cost of living issues, Boston ranks high on livability ratings, ranking 36th worldwide in quality of living in 2011 in a survey of 221 major cities.
ground_truth: among the top 30
sub_queries: Everfree >> author Answer: Nick Sagan
Nick Sagan >> place of birth Answer: Boston
What rank does Boston hold as far as being an economically powerful city in the world? Answer: among the top 30