Russia is the world's fourteenth-largest exporter. In 2016, the oil-and-gas sector accounted for 36% of federal budget revenues. In 2019, the Natural Resources and Environment Ministry estimated the value of natural resources to 60% of the country's GDP. Russia has one of the lowest external debts among major developed countries, and ranked high among the "very easy" countries in the 2019 Ease of Doing Business Index. It has a flat tax rate of 13%, and has the world's second-most attractive personal tax system for single managers after the United Arab Emirates. However, extreme inequality of household income and wealth in the country has also been noted.