Using irrigation to increase dry season production would therefore reduce the labour devoted to these other activities and so reduce the income they provide, rather than supplementing it. The cultivated land is relatively unproductive: paddy fields produce only 424 tonnes of rice per square mile, compared to 547 nationally. Most farmers can produce only one crop of rice a year. Many farmers still use water buffalo rather than tractors. Sixty percent of cultivated land is devoted to rice paddies. The concentration on rice farming has made the farmers vulnerable to fluctuating prices. This has been reduced somewhat by increased diversification, but Isan still accounts for half of Thailand's exports of rice, cassava, and sugar. These crops employ 700,000 Isan families. Other crops include, tobacco, cotton, and watermelons. Tourism According to the governor of Nakhon Phanom Province, "The entire Northeast [Isan] gained only 2.9 percent of [the] country's tourism income of 2.7 trillion baht [in 2017]." Other sectors Other sectors of the economy have been growing more quickly than agriculture, although this growth can be misleading. The number of factories grew from 1,908 in 1975 to 44,000 in 1995, but 34,312 of these were rice mills. In 2000, 76 percent of Isan factories were breweries or food or tobacco processors. A study conducted by Khon Kaen University estimated that each year 8.67 billion baht is sent by foreign husbands to their wives in Isan. The 2010 census found that 90 percent of the slightly more than 27,000 foreigners living in the northeastern region were married to women from there. Poverty Isan's economic disadvantages have caused great poverty. Most of Thailand's rural poor live in Isan. In 1995, 28 percent of the population was classed as below the poverty line, compared to just seven percent in central Thailand. In 2000, per capita income was just 26,317 baht, compared to 208,434 in Bangkok. Even within Isan, there is a rural/urban divide. In 1995, all of Thailand's ten poorest provinces were in Isan, the poorest being Sisaket Province. In 2012, six of Thailand's ten poorest provinces were in Isan, Kalasin being the poorest province in the region. From 2000 to 2012, half of Thailand's eight provinces with chronic poverty were in Isan. Most wealth and investment is concentrated in the four major cities of Khorat, Ubon, Udon, and Khon Kaen. These four provinces account for 40 percent of the region's population. Workforce A survey