"The archbishop of Manila claimed in 1637 that Moro raiders from the south had seized an average of 10,000 Catholic Filipinos a year over the previous 30 years. Descriptive materials indicate fairly steady raiding, which might thus have yielded a total booty of some two million slaves in the first two centuries of Spanish rule after 1565. A shipping capacity calculation suggests that between 200,000 and 300,000 captives entered the Sulu sultanate from 1770-1870, lower than contemporary European estimates. However, Spanish and Dutch naval patrols became more effective from the 1840s, leading Moros to seize unquantified numbers of Animists in inland Mindanao."