Bornholm Regional Municipality is the local authority (Danish language, kommune) covering the entire island. It is the result of a merger of the five former (1 April 1970 until 2002) municipalities on the island (Allinge-Gudhjem Municipality, Hasle, Bornholm, Nexø, Rønne and Aakirkeby) and the former Bornholm County. Bornholm Regional Municipality was also a county in its own right during its first four years from 1 January 2003 until 31 December 2006. From 1 January 2007 all counties were abolished, and Bornholm became part of the Capital Region of Denmark whose main responsibility is the health service. The municipality still retains its name Bornholm Regional Municipality. The island had 21 municipalities until March 1970, of which 6 were market towns and 15 parishes. In addition to supervising parish municipalities, which was the responsibility of the counties in all of Denmark, the market town municipalities of Bornholm were supervised by Bornholm County as well and not by the Interior Ministry as was the case in the rest of Denmark. The seat of the municipal council is the islands main town, Rønne. The voters decided to merge the county with the municipalities in a referendum May 29, 2001, effective from January 1, 2003. The question on the ballot was, "Do you want the six municipal entities of Bornholm to be joined to form one municipal entity as of 1 January 2003?" 73.9% voted in favour. The lowest percentage for the merger was in Nexø municipality, whose mayor, Annelise Molin, a Social Democrat, spoke out against the merger. It was required that each municipality had more "Yes" votes than "No" votes. Otherwise the merger would have to be abandoned altogether. The six municipal entities had 122 councillors (of which county clls were 15) and the new regional municipality would have 27 councillors from the start. They were reduced to 23 from 1 January 2018 (Danish local elections, 2017). The merger was approved in a law by the Folketing 19 March 2002, transferring the tasks of the abolished county and old municipalities to the new Bornholm Regional Municipality. The first regional mayor in the first three years from 2003 until 2005 was Thomas Thors (born 28 July 1949), a physician and member of the Social Democrats (Denmark) and previously the last mayor of Rønne Municipality for five years from 1998 until 2002. Bjarne Kristiansen, who was the last mayor of Hasle, Bornholm 2½ years from the summer of 2000 until 2002, representing the local Borgerlisten political party, served as mayor for four years from January 1, 2006 until 2009. From January 1, 2007, Bornholm became a part of the Capital Region of Denmark. From January 1, 2010 the mayor has been Winni Grosbøll, a high school teacher and a member of the Social Democrats (Denmark) (Socialdemokratiet) Politics of Denmark.
Answer this question: How many municipalities did the island have that weren't in market towns?
15