The population of Padang in 1920 was 28,754, the second largest city in Sumatra behind Palembang. At the time of independence in the 1940s the city had around 50,000 inhabitants. Coffee was still important, but copra was also a major item produced by farmers in its hinterland. The population growth since then has been partly a result of growth in the area of the city, but largely is a result of the migration to major cities seen in so many developing nations. From 1950 the Ombilin coal field developed with Padang as its outlet port. This was seen by some observers as reflecting the economic and political colonisation of Indonesia.