Further, quantity-based interventions are typically easier to administer than more complex price-based incentives, making them particularly useful tools for countries with weak administrative capacity. Many of these instruments are already utilized by developing countries. Green investment tax credits are used in 18 developing countries, public investment is used in 17, while feed-in tariffs, which guarantee prices to clean energy producers above the existing market price, are used in 17, including Algeria, Mongolia, Sri Lanka and Uganda (REN21, 2010). Many of these mechanisms have been criticized for locking in subsidies that then become politically difficult to remove, although putting time limits on them can help reduce this risk somewhat.