There remains sizeable theoretical debate about the causes, effects and alternatives for unemployment. Traditional economics, neoclassical economics, and the Austrian School of economics claim that market mechanisms are reliable method of resolving unemployment.  These theories dispute against interventions imposed on the labour market from the outside, such as unionization, minimal wage laws, taxes, and other rules that they claim discourage the hiring of personnel. Keynesian economics stresses the cyclical nature of unemployment and recommends interventions it remarks will reduce unemployment during recessions. This theory targets recurrent supply shocks that out of the blue reduce aggregate demand for goods and services and so reduce demand for staff.