Despite limited natural resources, intensive development of the agricultural and industrial sectors over the past decades has made Israel largely self-sufficient in food production, apart from grains and beef. Imports to Israel, totaling $66.76 billion in 2017, include raw materials, military equipment, investment goods, rough diamonds, fuels, grain, and consumer goods. Leading exports include machinery and equipment, software, cut diamonds, agricultural products, chemicals, and textiles and apparel; in 2017, Israeli exports reached $60.6 billion. The Bank of Israel holds $113 billion of foreign-exchange reserves. Since the 1970s, Israel has received military aid from the United States, as well as economic assistance in the form of loan guarantees, which now account for roughly half of Israel's external debt. Israel has one of the lowest external debts in the developed world, and is a lender in terms of net external debt (assets vs. liabilities abroad), which  stood at a surplus of $69 billion.