Hon DAVID PARKER: The four basic principles of any decent tax system are horizontal equity—people in the same economic position pay the same amount of tax—vertical equity, that people that are better off at least pay the rate that people that are worse off than them—should be progressive. It should be administratively efficient, for both the tax department and taxpayers, and it should minimise the distortions that are caused to the economy, or can be caused by improper tax systems. In respect of the principle that this most addresses, it's the vertical equity issue. 