These mandates take the form of intergovernmental regulations, grant conditions, prohibition of actions contrary to national policy (so-called "pre-emptions") and, in some cases, significant under-estimates of the true costs of (in principle) funded mandates. Reforms to curb or eliminate unfunded mandates are often limited in scope and may erode over time as new cost-shifting mechanisms are employed (OECD, 2010c). While mandates are often legitimate tools of policy and may help curtail harmful forms of inter-jurisdictional competition, address spillovers that go beyond the jurisdiction (externalities) or ensure conformity with national priorities, they can also distort local government spending priorities and put local budgets (and thus service provision and investment) under strain. Closely linked to this is the question of the degree of control that local governments have over their own spending: in many countries, the share of “mandatory spending” based on national legislation is rather high.