Chapter 4 | Page 148 purchases and sales of equity shares are also levied in some countries.37 While the efficacy and effectiveness of these taxes in raising revenue and their overall impact on the economy may be country-specific, all these revenue tools represent opportunities for developing countries to maximise public sector revenue. 4.2.2 Non-tax revenue In addition to the tax-based revenue sources identified above, the State can raise revenue through a number of non-tax sources. These include revenues collected through royalties, profits and dividends from public sector enterprises, revenue from lease of land and other natural resources, sovereign wealth funds, and reserves held by the government and the central bank. All these sources can further support the State to fulfil human rights obligations. Revenues from natural resource exploitation/extraction are obtained through a variety of instruments, including royalties, profit or rent taxes, production sharing arrangements, auction of exploration and production leases, excise and trade taxes, production by State-owned firms, and State participation through paid-up equity or carried interest.38 Forms of mining or extractive industries royalties include: unit based royalties; ad valorem royalties; profitbased royalties; tax on economic rent; hybrid systems combining the above systems; and other methods such as production sharing.39 Many States are also establishing special revenue/royalty arrangements with resource sectors such as mining, oil and gas to expand the State revenue stream. In Peru, for example, mining levies have been expanded and the proceeds used for 37 See for example, Ortiz, Chai and Cummins, above n 9. 38 Robin Boadway and Michael Keen, 'Rent Taxes and Royalties in Designing Fiscal Regimes for Non-Renewable Resources' (CESIFO Working Paper No. 4568, CESIFO, January 2014), 2. 39 International Mining for Development Centre, 'Mineral royalties and other mining-specific taxes' (Policy Paper, IMDC, 2012), <http://www.eisourcebook.org/cms/March_2013 /Mineral%20royalties%20%26%20other%20mining-specific%20taxes.pdf>. The special mining royalties are often directed on the net value of the mineral resources which are often levied at the project level, rather than at the consolidated entity level, after deducting the cost of production.