The Greens have a policy of approving no new thermal coal or unconventional gas projects in Australia. That includes new mines, as well as expansions to existing mines. In 2013 the party obtained costings from the parliamentary budget office detailing their estimate of how much revenue the federal budget would lose as a result of reduced tax and any other costs, if the policy was implemented. It was then estimated the policy would result in the government missing out on $1.5bn over the forward estimates – the four years to July 2017. The Greens asked for the same advice again this year and that figure dropped dramatically to just $290m over the forward estimates – the four years to July 2019.