Initially, most of the immigrants were miners originating from Sambas in neighbouring Dutch Borneo. These later formed a Kongsi system in Bau. The second Rajah continued this policy, particularly targeting the agricultural sector. Conflicts ensued between the government and the Chinese in 1857, believed to have arisen, inter alia, in relation to the Second Opium War. There was no forced labour, except for prisoners during public works and roads repair. In contrast to Dutch East Indies's forced cultivation system (cultuurstelsel), the indigenous people of Sarawak paid only a small amount of door tax and land rent. Companies Borneo Company Limited was formed in 1856. It was involved in a wide range of businesses in Sarawak, including trade, banking, agriculture, mineral exploration and development. The second Rajah worked to stabilise the economy and reduce government debt. The economy grew significantly under his reign, with total exports reaching $386,439 and imports $414,756 in 1863. Land The Rajah established the land tenure policy in 1863 with some minor modifications throughout Brooke's rule. Every inhabitant in Sarawak was entitled to three acres of land, in which sale was prohibited, and no one would own more than 100 acres without the permission of the government. Although the majority of the lands were in smallholders, the Brooke government granted several land concessions to Borneo Company Limited to develop rubber, timber, oil, coal, and antimony. Agriculture In 1869, by which time total trade had reached $3,262,500, the second Rajah invited Chinese black pepper and gambier growers from Singapore to cultivate their crops in Sarawak. As a result, by the early 20th century, Sarawak became one of the world's major producers of pepper. The kingdom was a relative latecomer to the natural rubber boom due to the reluctance of the second Rajah to give over indigenous farmland to European companies. In 1910, Rajah declined offers by five foreign companies to set up large-scale rubber plantations here because speculation of rubber prices was "a mania at the present which did not suit the quiet non-speculative spirit of the country". Only five large rubber estates were established during his reign. Oil reserves were discovered in his final years. From the 1930s, through the work of the Chinese businesses in the kingdom, it became a significant raw material supplier, with Singapore as a major trading partner. Currency A Sarawak dollar was first issued in 1858 and remained at par with the