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. Between 1914 and 1930, an estimated 10,000 Liberians went to Fernando Po under a labour treaty that was stopped altogether in 1930.