From the Great Recession, Czech Republic is in stagnation or decreasing of GDP. Some commenters and economists criticising fiscally conservative policy of Petr Nečas right-wing government, especially criticising ex-minister of finance, Miroslav Kalousek. Miroslav Kalousek in a 2008 interview, as minister of finance in the center-right government of Mirek Topolánek, said "Czech Republic will not suffer by financial crisis". In September 2008, Miroslav Kalousek formed state budget with projection of 5% GDP increase in 2009. In 2009 and 2010, Czech Republic suffered strong economical crisis and GDP decreased by 4,5%. From 2009 to 2012, Czech Republic suffered highest state budget deficits in history of independent Czech Republic. From 2008 to 2012, the public debt of Czech Republic increased by 18,9%. Most decrease of industrial output was in construction industry (-25% in 2009, -15,5% in 2013). From 4Q 2009 to 1Q 2013, GDP decreased by 7,8%.
Question: How many years did it take for the public debt of Czech Republic to increase by 18,9%?
Answer: 4