Since the mid-1980s, farm sizes and food production have been decreasing, due in part to the resettlement of displaced people. Despite Rwanda's fertile ecosystem, food production often does not keep pace with population growth, and food imports are required. Crops grown in the country include coffee, tea, pyrethrum, bananas, beans, sorghum and potatoes. Coffee and tea are the major cash crops for export, with the high altitudes, steep slopes and volcanic soils providing favourable conditions. Reliance on agricultural exports makes Rwanda vulnerable to shifts in their prices. Agricultural animals raised in Rwanda include cows, goats, sheep, pigs, chicken, and rabbits, with geographical variation in the numbers of each. Production systems are mostly traditional, although there are a few intensive dairy farms around Kigali. Shortages of land and water, insufficient and poor-quality feed, and regular disease epidemics with insufficient veterinary services are major constraints that restrict output. A "One Cow per Poor Family Programme" (Girinka), implemented in 2006, distributed 341,065 cows in 2018. Fishing takes place on the country's lakes, but stocks are very depleted, and live fish are being imported in an attempt to revive the industry. Rwanda's mining industry is an important contributor, generating US$93 million in 2008. Minerals mined include cassiterite, wolframite, sapphires, gold, and coltan, which is used in the manufacture of electronic and communication devices such as mobile phones. Production of methane from Lake Kivu began in 1983, but to date has been used only by the Bralirwa Brewery. In 2019, the country was the 7th largest world producer of tungsten and the 12th largest world producer of tin. Energy and electrification Rwanda has made tremendous strides in improving electrification in the 21st century. A great number of new areas has become electrified through an expansion of infrastructure. Depletion of the forests will eventually pressure Rwandans to turn to fuel sources other than charcoal for cooking and heating. Given the abundance of mountain streams and lakes, the potential for hydroelectric power is substantial. Rwanda is exploiting these natural resources through joint hydroelectric projects with Burundi and the Democratic Republic of the Congo. Industry The industrial sector is growing, contributing 16% of GDP in 2012. Rwanda's manufacturing sector is dominated by the production of import substitutes for internal consumption. The larger enterprises produce beer, soft drinks, cigarettes, hoes, wheelbarrows, soap, mattresses, plastic pipe, roofing materials, and bottled water. Other products manufactured include agricultural products, small-scale beverages, soap,