Between 1926 and 1959 Bioko and Rio Muni were united as the colony of Spanish Guinea. The economy was based on large cacao and coffee plantations and logging concessions and the workforce was mostly immigrant contract labour from Liberia, Nigeria, and Cameroun. Military campaigns were mounted to subdue the Fang people in the 1920s, at the time that Liberia was beginning to cut back on recruitment. There were garrisons of the colonial guard throughout the enclave by 1926, and the whole colony was considered 'pacified' by 1929. However, Rio Muni had a small population, officially put at a little over 100,000 in the 1930s, and escape over the frontiers into Cameroun or Gabon was very easy. Moreover, the timber companies needed growing amounts of labour, and the spread of coffee cultivation offered an alternative means of paying taxes. Fernando Po thus continued to suffer from labour shortages. The French only briefly permitted recruitment in Cameroun, and the main source of labour came to be Igbo smuggled in canoes from Calabar and Oron, Nigeria. The persisting labour shortage in the cacao, coffee and logging industries was only overcome by the mushrooming illegal canoe-based smuggling of Igbo and Ibibio workers from the Eastern Provinces of Nigeria. The number of clandestine contract workers on the island of Fernando Po grew to 20,000 in 1942. A labour treaty was signed in the same year, and a continuous stream of workers arrived in Spanish Guinea. It was this treaty which really permitted Fernando Po to become one of Africa's most productive agricultural areas after the Second World War. By 1968 there were almost 100,000 Nigerians in Spanish Guinea.