Many agribusinesses and food processors source raw materials from smallholder farmers. Important local crops include corn and some smallholder plantation crops such as coffee. Netting studied sustainability and intensive agriculture in smallholder systems through history. In Africa there are smallholder cooperatives and plantations which produce Fair Trade certified tea. The crop is grown in Ivory Coast mostly by smallholder farmers planting on 1-3 hectares. Smallholder farming accounts for 80 percent of the country's cereal production. In 2013, Thailand had 5.9 million smallholder farming households. Approximately 70% of the world's food is produced by 500 million smallholder farmers . In 1975, there were 4.2 million smallholder farming households in Thailand. Smallholder farms account for 80% of cultivated lands in sub-Saharan Africa. A majority of the population remains dependent on smallholder cash crop production. There is some smallholder cultivation of tobacco. There are about 3,000 smallholder irrigation schemes covering a total area of 47,000 ha. Smallholder arrangements prompted widespread government investment in education. Tea planting under smallholder conditions has become popular in the 1970s.