When the 2012 national census was taken, the city had a population of 4,364,541, about ten percent of the country's total. The average private household size was 3.9 persons compared to the national average of 4.7. Less than half of the city's residents were married, with a rate lower than any other region in the country. The literacy rate in the city was 96%, while the national average was 78%). Between the 2002 and 2012 censuses, the city's 5.6% average annual growth rate was the highest in the country.