The French began building canals and draining lands in the Mekong delta to increase cultivation. The vast system of irrigation works-canals and earthworks-built mainly with forced labour, increased rice production and allowed the export of rice to the international market. The area under rice cultivation went up from 2,74,000 hectares in 1873 to 1.1 million hectares in 1900 and 2.2 million hectares in 1930. Vietnam exported two-thirds of its rice production and by 1931 had become the third largest exporter of rice in the world.