Between 1961 and 1980, the population of Jakarta doubled and during the period 1980–1990, the citys population grew annually by 3.7%. The 2010 census counted some 9.58 million people, well above all government estimates. The population has risen from 4.5 million in 1970 doubled to 9.5 million in 2010, counting only its legal residents, while the population of Jabodetabek has risen from 8.2 million in 1970 jumping to 28.5 million in 2010. According to the governments Jakarta in Figures document, the population stood at 10,187,595 in 2011 and 9,761,407 in 2012. As per 2014, the population of Jakarta stood at 10,075,310 people. with a population density of 15,174 people/km2. As per 2014, the population of Jabodetabek was 30,326,103, accounting for 11% of Indonesias overall population. The gender ratio was 102.8 (males per 100 females) in 2010 and 101.3 in 2014.
Question: How many years passed that the Jakarta doubled between 1961-1980?
Answer: 19