"There are no statistics on the overall number of slaves imported into Jolo in the period under consideration, except the estimates of European observers. These range from 750 to as high as 4,000 captives a year for the Philippines alone from 1775 to 1848. .... Slave imports to the Sulu Sultanate during the first sixty-five years probably averaged between 2,000 and 3,000 a year. The steepest rise in the number of slaves annually brought to Sulu, between 3,000 and 4,000, occurred in the period 1836-48, during which foreign trade was most intense at Sulu. The trade reached its apex in 1848 and slackened considerably in the next two decades, with imports ranging between 1,200 and 2,000 slaves a year until it collapsed in the 1870s.' The figures appear to show that between 200,000 and 300,000 slaves were moved in Iranun and Samal vessels to the Sulu Sultanate in the period 1770-1870."