The Berlin Conference of 1885 ceded control of the Congo Free State to King Leopold II as his private possession. From around 1900 there was growing international concern for the extreme and savage treatment of the Congolese population under Leopold II, for whom the Congo was primarily a source of revenue from ivory and rubber production. Many Congolese were killed by Leopold's agents for failing to meet production quotas for ivory and rubber. In 1908, this outcry led the Belgian state to assume responsibility for the government of the colony, henceforth called the Belgian Congo. A Belgian commission in 1919 estimated that Congo's population was half what it was in 1879.