About three-quarters were smallholders on Native Trust Land, the rest estate tenants. Numbers declined later, but there were still 70,000 in 1965, producing 12,000 tons. Although the value of tobacco exports continued to rise, they decreased as a proportion of the total after 1935 because of the increased importance of tea. Egyptian cotton was first grown commercially by African smallholders in the upper Shire valley in 1903 and spread to the lower Shire valley and the shores of Lake Nyasa. By 1905 American Upland cotton was grown on estates in the Shire Highlands. African-grown cotton was bought by British Central Africa Company and the African Lakes Corporation until 1912 when government cotton markets were established where a fairer price for cotton was given. Reckless opening-up of unsuitable land by inexperienced planters had led to 22,000 acres of cotton in 1905, but 140 tons were exported. Halving of the area to 10,000 acres and improving quality made cotton more important, to a peak of 44% of export value in 1917 when the First World War stimulated demand to 1,750 tons. A shortage of manpower and disastrous floods in the lower Shire valley caused a drop in production to 365 tons in 1918. It was not until 1924 that the industry recovered, reaching 2,700 tons in 1932 and a record of 4,000 tons exported in 1935. This was mainly African production in the lower Shire valley, as output from European estates became insignificant. The relative importance of cotton exports dropped from 16% of the total in 1922 to 5% in 1932, then rallied to 10% in 1941, falling to 7% in 1951. The quality of cotton produced improved from the 1950s with stricter controls on pests and, although 80% of the crop continued to be grown in the lower Shire valley, it also began to be grown in the northern shore of Lake Malawi. Production varied widely, and increasing amounts were used domestically, but at independence cotton was only the fourth most valuable export crop. Tea was first exported from Nyasaland in 1904 after tea plantations were established in the high rainfall areas of Mlanje District, later extended into Cholo District. Exports steadily increased from 375 tons in 1922 to 1,250 tons in 1932, from 12,600 acres planted. The importance of tea increased dramatically after 1934, from only 6% of total exports in 1932 to over 20% in 1935. It never fell below that level, rising to over 40% from 1938 to 1942, and in the three years 1955, 1957 and 1960 the value of tea exports exceeded that of tobacco and until the mid-1960s, Nyasaland had the most extensive area of tea cultivation in Africa.