The population is concentrated in the Andean highlands and along the Caribbean coast, also the population densities are generally higher in the Andean region. The nine eastern lowland departments, comprising about 54% of Colombia's area, have less than 6% of the population. Traditionally a rural society, movement to urban areas was very heavy in the mid-20th century, and Colombia is now one of the most urbanized countries in Latin America. The urban population increased from 31% of the total in 1938 to nearly 60% in 1973, and by 2014 the figure stood at 76%. The population of Bogotá alone has increased from just over 300,000 in 1938 to approximately 8 million today. In total seventy-two cities now have populations of 100,000 or more (2015).  Colombia has the world's largest populations of internally displaced persons (IDPs), estimated to be up to 4.9 million people.